2024-03-29T11:10:15Z
http://ir.lib.uwo.ca/do/oai/
oai:ir.lib.uwo.ca:civilpub-1006
2009-06-27T01:36:02Z
publication:civil
publication:faculties
publication:civilpub
Variability of Point Source Infiltration Rates for Two-Phase Flow in Heterogeneous Porous Media
Kueper, Bernard H.
Gerhard, Jason I.
This study examines the influence of source release location, size, and strength on the infiltration rate and degree of lateral spreading of a dense nonwetting liquid infiltrating into an initially wetting liquid saturated, heterogeneous porous medium. It is demonstrated through numerical simulation in 25 realizations of a spatially correlated random hydraulic conductivity field that infiltration rates for point source releases are lognormally distributed with a variance equal to that of the underlying hydraulic conductivity distribution. The variability in infiltration rates is shown to decrease for sources larger than the correlation scale of hydraulic conductivity. In all cases, individual infiltration rates showed no tendency to converge to the ensemble average. A moment analysis demonstrates that the degree of lateral spreading of the nonwetting body for individual realizations varied greatly and also did not display a tendency to converge to an ensemble average. Numerical simulations carried out in an equivalent homogeneous porous medium incorporating large-scale anisotropy of intrinsic permeability provided infiltration rates below the ensemble average. For point source releases the degree of lateral spreading exhibited in the equivalent homogeneous porous medium was below the entire ensemble of heterogeneous results. A series of 10 simulations conducted in a single realization demonstrates that the degree of lateral spreading (second moment) along main drainage is a function of the average nonwetting phase saturation with greater degrees of lateral spreading at low capillary pressures. The practical implication of this study is that in addition to fluid and media properties the specific order of encounter of varying permeability lenses must be known in the immediate vicinity of a nonwetting phase release if infiltration rates are to be accurately predicted.
1995-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/1
http://www.agu.org/pubs/crossref/1995/95WR02329.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
Point Source Infiltration
Two-Phase Flow
Heterogeneous Porous Media
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1005
2009-06-27T01:29:24Z
publication:civil
publication:faculties
publication:civilpub
Capillary Pressure Characteristics Necessary for Simulating DNAPL Infiltration, Redistribution, and Immobilization in Saturated Porous Media
Gerhard, J. I.
Kueper, B. H.
This study presents a capillary-pressure saturation (PC-S) constitutive model that incorporates the capillary phenomena necessary for simulating the spatial distribution of nonwetting fluid migrating in a saturated porous medium. To develop a model validation data set, a sequence of dense, nonaqueous phase liquid (DNAPL) pools were emplaced, under alternating drainage and imbibition conditions, in a one-dimensional, 1 m tall, saturated sand pack. A light transmission/image analysis system successfully distinguished between connected-phase and residual nonwetting fluid in the apparatus, thereby permitting the accurate measurement of DNAPL pool heights. These heights are found to depend on the nonzero capillary pressure across the fluid-fluid interface at the top of the pool. The terminal pressure is demonstrated to be the minimum sustainable capillary pressure in connected-phase nonwetting fluid experiencing imbibition, below which residual is formed. Additional bench-scale experiments demonstrate that a nonwetting phase pool will penetrate an underlying capillary barrier when the entry pressure is exceeded and that the resulting infiltration will terminate when the capillary pressure at the barrier reduces to the terminal pressure. At the macroscopic scale the terminal pressure corresponds to the extinction saturation (i.e., zero nonwetting phase flow) at the inflection point on the imbibition PC-S curve. A ratio of terminal to entry pressure of approximately 0.6 is found to apply at both bench and macroscopic scales and to be independent of porous media and fluid properties. The developed PC-S constitutive model, which extends the Brooks-Corey function to incorporate the terminal pressure, successfully predicted the behavior observed in the laboratory experiments. Constitutive models that do not incorporate both an entry and a terminal pressure, such as those based upon the standard van Genuchten function, are demonstrated to be unable to predict the observed equilibrium DNAPL pool heights in homogeneous media or above capillary barriers.
2003-08-14T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/2
http://www.agu.org/pubs/crossref/2003/2002WR001270.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
multiphase flow
capillary pressure
constitutive relationships
DNAPL
terminal pressure
entry pressure
Groundwater hydrology
Groundwater transport
Stochastic processes
Instruments and techniques
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1004
2009-06-27T01:30:30Z
publication:civil
publication:faculties
publication:civilpub
Relative Permeability Characteristics Necessary for Simulating DNAPL Infiltration, Redistribution, and Immobilization in Saturated Porous Media
Gerhard, J. I.
Kueper, B. H.
This study presents a relative permeability-saturation (kr-S) constitutive model that incorporates the critical phenomena necessary for simulating the rates of nonwetting fluid infiltration, redistribution, and immobilization in a saturated porous medium. To develop a model validation data set, the migration of a dense, nonaqueous phase liquid (DNAPL) pool within a one-dimensional, 1 m tall, saturated sandpack was monitored under alternating drainage and imbibition conditions. A light transmission/image analysis system, able to distinguish between connected-phase and residual nonwetting phase (NWP) in the apparatus, measured the elevation of the top of the connected-phase DNAPL pool as a function of time. Light transmission calibration curves, correlating fluid saturation to transmitted color at the macroscopic scale, were found to exhibit a functional dependence on saturation history that must be taken into account. Applying the calibration curves to captured images of the experiment provided a continuous sequence of fluid saturation profiles. Numerical simulations of the bench-scale experiment, using model parameters measured independently at the macroscopic scale, predict within measurement uncertainty the observed timescales of DNAPL migration and immobilization. Additional simulations reveal that model validation for imbibition processes depends on properly accounting for NWP kr-S hysteresis, including imbibition function curvature and the abrupt extinction of NWP relative permeability.
2003-08-14T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/3
http://www.agu.org/pubs/crossref/2003/2002WR001490.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
multiphase flow
relative permeability
constitutive relationships
DNAPL
tortuosity
Groundwater quality
Groundwater transport
Instruments and techniques
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1003
2009-06-27T01:16:58Z
publication:civil
publication:faculties
publication:civilpub
Influence of Constitutive Model Parameters on the Predicted Migration of DNAPL in Heterogeneous Porous Media
Gerhard, J. I.
Kueper, B. H.
This study examines the influence of constitutive models and their parameters on predictions of the spatial and temporal distribution of a finite release of a dense, nonaqueous phase liquid (DNAPL) into a two-dimensional, spatially correlated random permeability field. The base case simulation employed a comprehensive constitutive model that was validated against relevant one-dimensional laboratory experiments. The base case was perturbed in the course of nine individual simulations, where each simulation examined the consequences of simplifying a single model characteristic. None of the nine subsequent simulations was able to reproduce, within ±10%, the spatial and temporal migration characteristics of the nonwetting fluid body at late time predicted by the base case. Capillary pressure-saturation relationships that do not incorporate specific displacement and terminal pressures are demonstrated to severely overpredict the spatial extent of nonwetting fluid advancement. This suggests that van Genuchten-based models may not be suitable for predicting DNAPL migration in saturated porous media. Not accounting for any one of hysteresis, nonwetting phase trapping, or the proper curvature or end-point values of the nonwetting phase imbibition relative permeability curve profoundly influenced the time predicted for all nonwetting fluid movement to cease. The practical implication of this study is that an appropriate, comprehensive constitutive model, characterized with suitable parameter values, is necessary to accurately simulate a complete DNAPL release below the water table in both space and time.
2003-10-08T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/4
http://www.agu.org/pubs/crossref/2003/2002WR001570.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
Groundwater transport
Groundwater hydrology
Instruments and techniques
multiphase flow
constitutive relationships
DNAPL
numerical modeling
capillary pressure
relative permeability
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1002
2009-06-27T01:09:46Z
publication:civil
publication:faculties
publication:civilpub
Simulating the Dissolution of a Complex Dense Nonaqueous Phase Liquid Source Zone: 1. Model to Predict Interfacial Area
Grant, G. P.
Gerhard, J. I.
A thermodynamically based model for predicting two-fluid interfacial area (IFA) within a porous medium as a function of wetting phase saturation (S W ) and saturation history is presented. The model considers consistency with multiphase flow constitutive relationships, the conversion of total to effective specific interfacial area, energy losses, and the change of interfacial area as residual nonwetting phase dissolves. The model requires as input only the capillary pressure–saturation relationships and porosity. Published, high-resolution interfacial area-saturation data sets were adequately reproduced when independent measures of these parameters were employed by the model. In particular, the model is found to reproduce key IFA(S W ) features including the IFA magnitude and S W value corresponding to the function's maximum, negligible IFA at residual S W and the observed hysteresis of IFA(S W ). Varying key model parameters reveals that the magnitude of the IFA(S W ) relationship is predicted to be linearly related to the porosity and entry pressure of the porous medium and is unaffected by interfacial tension. Interfacial area is a parameter in the single boundary layer expression of mass transfer between two immiscible liquids in porous media. The model's ability to predict local-scale IFA for a wide variety of fluid-fluid-porous media systems while accounting for saturation and saturation history thus provides an avenue for simulating the dissolution of complex source zones containing both pooled and residual dense nonaqueous phase liquids.
2007-12-20T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/5
Civil and Environmental Engineering Publications
Scholarship@Western
multiphase flow
DNAPL
rate-limited mass transfer
dissolution
interfacial area
thermodynamic model
Groundwater hydrology
Groundwater quality
Groundwater transport
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1001
2009-06-27T01:05:24Z
publication:civil
publication:faculties
publication:civilpub
Simulating the Dissolution of a Complex Dense Nonaqueous Phase Liquid Source Zone: 2. Experimental Validation of an Interfacial Area–based Mass Transfer Model
Grant, G. P.
Gerhard, J. I.
A multiphase flow–aqueous phase transport numerical model (DNAPL3D-MT) is developed to simulate the dissolution of complex source zones containing both pooled and residual dense nonaqueous phase liquids (DNAPLs). The multiphase flow model (DNAPL3D) is coupled to the aqueous species transport code (MT3D) via a flexible mass transfer function, which can employ the local equilibrium assumption or the single–boundary layer expression for rate-limited dissolution either incorporating a lumped (correlation function) coefficient or explicitly accounting for the interfacial area (IFA) between the fluids. For the latter, this work employs the thermodynamically based Explicit IFA Submodel (Grant and Gerhard, 2007), which provides IFA as a function of saturation and saturation history. A bench-scale experiment is presented involving the complete, natural dissolution of a DNAPL source zone emplaced by a point source release into heterogeneous porous media. DNAPL3D-MT simulations of the experiment, involving no calibration to results, are compared with the observed evolution of both (1) measured downgradient dissolved phase concentrations and (2) DNAPL source zone configuration. The model, employing a mass transfer expression equipped with the Explicit IFA Submodel, simulates the experiment more accurately than when equipped with either a local equilibrium assumption or a published empirical correlation expression. Sensitivity simulations indicate that this model validation is sensitive to a number of the key assumptions in the Submodel derivation except one: the relationship between interfacial area and residual DNAPL saturations. The employed assumption of a single mass transfer coefficient value is supported by an analysis of the evolution of Peclet numbers throughout the DNAPL source zone, which reveals that the low hydraulic gradient employed resulted in diffusion-dominated mass transfer conditions throughout the experiment. This study suggests that simulations of global mass flux from complex DNAPL source zones are sensitive to the interrelationship of rate-limited mass transfer and groundwater velocity (and thus aqueous phase relative permeability and DNAPL saturation) at the local scale.
2007-12-20T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/6
http://www.agu.org/pubs/crossref/2007/2007WR006039.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
multiphase flow
DNAPL
rate-limited mass transfer
dissolution
interfacial area
thermodynamic model
Groundwater hydrology
Groundwater quality
Groundwater transport
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1000
2009-06-27T00:59:21Z
publication:civil
publication:faculties
publication:civilpub
Modeling U(VI) Biomineralization in Single- and Dual-porosity Porous Media
Rotter, B. E.
Barry, D. A.
Gerhard, J. I.
Small, J. S.
Uranium extraction, processing, and storage have resulted in a legacy of uranium-contaminated groundwater aquifers worldwide. An emerging remediation technology for such sites is the in situ immobilization of uranium via biostimulation of dissimilatory metal-reducing bacteria (DMRB). While this approach has been successfully demonstrated in experimental studies, advances in understanding and optimization of the technique are needed. The motivation of this work was to understand better how dual-porosity (DP) porous media may affect immobilization efficiency via interactions with the dominant geochemical and microbial processes. A biogeochemical reactive transport model was developed for uranium immobilization by DMRB in both single- and dual-porosity porous media. The impact that microbial residence location has on the success of biostimulated U(VI) immobilization in DP porous media was explored under various porosity and mass transfer conditions. Simulations suggest that DP media are likely to show delayed U(VI) immobilization relative to single-porosity systems. U(VI) immobilization is predicted to be less when microbial activity is restricted to diffusion-dominant regions but not when restricted to advective-dominant regions. The results further highlight the importance of characterizing the bioresidency status of field sites if biogeochemical models are to predict accurately remediation schemes in physically heterogeneous media.
2008-08-26T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/7
http://www.agu.org/pubs/crossref/2008/2007WR006301.shtml
Civil and Environmental Engineering Publications
Scholarship@Western
remediation
uranium
reactive transport
subsurface
model
dissimilatory metal-reducing bacteria
Bioremediation
Modeling
Contaminant
organic biogeochemistry
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1008
2009-07-01T00:26:24Z
publication:civil
publication:faculties
publication:civilpub
Field Scale Impacts of Spatially Correlated Relative Permeability in Heterogeneous Multiphase Systems
Grant, G. P.
Gerhard, J. I.
Kueper, B. H.
Two-dimensional numerical simulations of two-phase (DNAPL-water) flow in spatially correlated random fields demonstrate the influence of nonwetting phase (NWP) relative permeability–saturation (kr,N–SW) relationships correlated to porous media intrinsic permeability (k). Both the volume of porous media invaded by the NWP and the length of time during which the NWP is migrating are under predicted if kr,N–k correlation is not accounted for in the model formulation. Not accounting for the kr,N–k correlation resulted in under predicting the volume of porous media invaded by up to approximately 10%, which is likely not significant for many practical applications. However, not accounting for the kr,N–k correlation resulted in under predicting field scale migration times by up to a factor of 4, which is likely significant in that the migration times are on the order of years to several decades for the DNAPL (1,2-DCE) considered in this study. The under prediction of migration times was greater for lower permeability aquifers.
2007-05-01T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/8
http://dx.doi.org/10.1016/j.advwatres.2006.10.005
Civil and Environmental Engineering Publications
Scholarship@Western
Relative permeability
DNAPL
Numerical modeling
Contaminant migration rates
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1007
2009-07-01T00:31:00Z
publication:civil
publication:faculties
publication:civilpub
The Influence of Precipitate Formation on the Chemical Oxidation of TCE DNAPL with Potassium Permanganate
West, Michael R.
Grant, Gavin P.
Gerhard, Jason I.
Kueper, Bernard H.
A three-dimensional two-phase flow model is coupled to a non-linear reactive transport model to study the efficacy of potassium permanganate treatment on dense, non-aqueous phase liquid (DNAPL) source removal in porous media. A linear relationship between the soil permeability (k) and concentration of manganese dioxide precipitate ([MnO2(s)]), k = ko + Srind [MnO2(s)], is utilized to simulate nodal permeability reductions due to precipitate formation. Using published experimental column studies, an Srind = −5.5 × 10−16 m2 L/mg was determined for trichloroethylene (TCE) DNAPL. This Srind was then applied to treatment simulations on three-dimensional TCE DNAPL source zones comprising either DNAPL at residual saturations, or DNAPL at pooled saturations.
DNAPL dissolution without oxidation treatment, simulated using equilibrium and the Nambi and Powers [Nambi I, Powers S. Mass transfer correlations for non-aqueous phase liquid dissolution from regions with high initial saturations. Water Resour Res 2003;39(2):1–11, SBH 4] mass transfer expression, required 31 and 36 years, respectively, to eliminate the residual source zone. For equilibrium dissolution with continuous treatment and no precipitate influence (Srind = 0 m2 L/mg), the residual source zone was removed after 11 years. However, when considering the precipitate influence (i.e., Srind = −5.5 × 10−16 m2 L/mg), 21 years of treatment were necessary to remove the DNAPL. When considering pulse treatments of 1 and 2 years duration followed by only dissolution, approximately 36 and 38 years, respectively, were required before the source zone was depleted, suggesting that there is no benefit to pulse treatment. Similar trends were observed when allowing 10 years of dissolution prior to treatment initiation. The treatment behaviour of the pooled TCE source, while slightly more efficient than the residual saturation source, was similar.
Based on simulation findings, the precipitate (rind) formation significantly influences DNAPL treatment with permanganate; the most significant reductions in efficacy were observed for single pulse treatments (of 1 and 2 years), which exhibited times to source depletion similar to the case of dissolution without treatment.
2008-02-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/9
http://dx.doi.org/10.1016/j.advwatres.2007.08.011
Civil and Environmental Engineering Publications
Scholarship@Western
Porous media
In situ chemical oxidation
Trichlorethene
Permanganate
Remediation
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1010
2009-07-04T02:19:18Z
publication:civil
publication:faculties
publication:civilpub
The Influence of Waterflood Design on the Recovery of Mobile DNAPLs
Gerhard, Jason I.
Kueper, Bernard
Hecox, Gary
This study examines the effectiveness of various waterflooding strategies to recover pooled dense nonaqueous phase liquid (DNAPL) from the subsurface at an industrial facility. The relative influence of horizontal injection/recovery well configuration, established hydraulic gradient, and fluid properties is investigated for a site characterized by a homogeneous silty sand underlain by an impermeable clay layer. The top of the clay layer is located 5 m below the water table and supports a laterally extensive 2 m deep DNAPL pool. The sensitivity study employs a two-phase flow numerical model that simulates both DNAPL infiltration and redistribution, including the formation of immobilized DNAPL residual. This is accomplished with constitutive relations featuring hysteretic capillary pressure-saturation pathways in which the local amount of residual formed is a function of the maximum non-wetting saturation attained during infiltration. Sixteen simulations, performed in two-dimensional vertical cross-section, demonstrate that strategies effecting increased wetting phase gradients, namely increasing drawdown at the recovery drain, adding injection wells, and reducing their distance to the recovery drain, result in an increased DNAPL volume recovered with time at the expense of increased volumes of ground water removed per unit volume of DNAPL recovered. Strategies which do not increase wetting phase gradients result in DNAPL recovery with a minimum volume of produced contaminated ground water. Three pulsed pumping simulations indicate that increasing the length of pump shut-down time decreases the recovery of DNAPL with time but increases efficiency with respect to ground water pumped. Decreased nonwetting density and increased interfacial tension result in poorer DNAPL recovery with respect to both time and volume of ground water removed, while reduced nonwetting viscosity corresponds to dramatically increased efficiency in both respects.
1998-03-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/10
http://www3.interscience.wiley.com/journal/119106719/abstract
Civil and Environmental Engineering Publications
Scholarship@Western
Waterflood
Mobile DNAPL
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1009
2009-07-04T02:09:39Z
publication:civil
publication:faculties
publication:civilpub
Time Scales of DNAPL Migration in Sandy Aquifers Examined via Numerical Simulation
Gerhard, Jason I.
Pang, TiWee
Kueper, Bernard H.
The time required for dense nonaqueous phase liquid (DNAPL) to cease migrating following release to the subsurface is a valuable component of a site conceptual model. This study uses numerical simulation to investigate the migration of six different DNAPLs in sandy aquifers. The most influential parameters governing migration cessation time are the density and viscosity of the DNAPL and the mean hydraulic conductivity of the aquifer. Releases of between 1 and 40 drums of chlorinated solvent DNAPLs, characterized by relatively high density and low viscosity, require on the order of months to a few years to cease migrating in a heterogeneous medium sand aquifer having an average hydraulic conductivity of 7.4 × 10−3 cm/s. In contrast to this, the release of 20 drums of coal tar (ρD= 1061 kg/m3, μD= 0.161 Pa·s) requires more than 100 years to cease migrating in the same aquifer. Altering the mean hydraulic conductivity of the aquifer results in a proportional change in cessation times. Parameters that exhibit relatively little influence on migration time scales are the DNAPL–water interfacial tension, release volume, source capillary pressure, mean aquifer porosity, and ambient ground water hydraulic gradient. This study also demonstrates that low-density DNAPLs (e.g., coal tar) give rise to greater amounts of lateral spreading and greater amounts of pooling on capillary barriers than high-density DNAPLs such as trichloroethylene or tetrachloroethylene.
2007-03-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/11
http://www3.interscience.wiley.com/journal/118538767/abstract
Civil and Environmental Engineering Publications
Scholarship@Western
DNAPL
migration
Numerical Simulation
sandy aquifer
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1012
2009-07-08T01:22:47Z
publication:civil
publication:faculties
publication:civilpub
Multidimensional Validation of a Numerical Model for Simulating a DNAPL Release in Heterogeneous Porous Media
Grant, Gavin P.
Gerhard, Jason I.
Kueper, Bernard H.
A fixed-volume release of 1,2-DCE, tracked in space and time with a light transmission/image analysis system, provided a data set for the infiltration, redistribution, and immobilisation of a dense non-aqueous phase liquid (DNAPL) in a heterogeneous porous medium. The two-dimensional bench scale flow cell was packed with a spatially correlated, random heterogeneous distribution of six sand types. In order to provide the necessary modelling parameters, detailed constitutive relationships were measured at the local scale for the six sands. These experiments revealed that nonwetting phase (NWP) relative permeability–saturation (krN–SW) relationships are strongly correlated to sand type. Trends in the best-fit krN–SW parameters reflected a positive correlation between mean grain diameter and the maximum NWP relative permeability, krNmax. Multiphase flow simulations of the bench scale experiment best reproduced the experimental observations, producing excellent matches in both time and space, when the measured, correlated local scale krN–SW relationships were employed.
2007-06-16T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/12
http://dx.doi.org/10.1016/j.jconhyd.2007.01.003
Civil and Environmental Engineering Publications
Scholarship@Western
Relative permeability
Multiphase flow
Nonwetting phase
Migration rates
Model validation
Constitutive relationships
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1011
2009-07-08T01:15:44Z
publication:civil
publication:faculties
publication:civilpub
Parameter and Process Significance in Mechanistic Modeling of Cellulose Hydrolysis
Rotter, B. E.
Barry, D.
Gerhard, J. I.
Small, J. S.
A process-based model relevant to landfill and anaerobic digesters was developed, which included a novel approach to biomass transfer between a cellulose-bound biofilm and biomass in the bulk liquid. Model results highlighted the significance of the bacterial colonization of cellulose particles by attachment through contact in solution. Simulations revealed that both enhanced colonization and cellulose degradation are associated with reduced cellulose particle size, increased biomass populations in solution and increased cellulose-binding ability of the biomass. This suggests that transportation of biomass into the system from elsewhere and/or bacterial inoculation of such systems could enhance degradation significantly. A sensitivity analysis of the system parameters revealed the biological rate and yield properties of the hydrolyzing bacteria are most significant with regard to cellulose degradation in the system.
2008-09-01T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/13
http://dx.doi.org/10.1016/j.biortech.2007.10.020
Civil and Environmental Engineering Publications
Scholarship@Western
Landfill
Degradation
Model
Biomass
Colonization
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1013
2009-07-09T00:31:02Z
publication:civil
publication:faculties
publication:civilpub
Site-Specific Design for Dual Phase Recovery and Stabilization of Pooled DNAPL
Gerhard, Jason I.
Kueper, Bernard H.
Hecox, Gary R.
Schwarz, Eric J.
Volume reduction and lowering of capillary pressure within a large DNAPL pool are utilized as objectives in the design of a large-scale dual phase recovery system at a chemical manufacturing facility in the United States. By reducing DNAPL pool height through mass removal, capillary pressure is lowered, resulting in a reduced potential for future vertical and horizontal mobilization of the chlorinated solvent DNAPL pool. The DNAPL pool extends over an approximately 200 m by 275 m area in low permeability fill deposits overlying a clay aquitard. A three-dimensional multiphase flow model was employed to arrive at a final design incorporating nine horizontal drains (total length 664 m) and a pulsed pumping system. The numerical model was calibrated to the results of a 42-day field pilot-test involving the removal of approximately 25,000 L of DNAPL from a single, 55 m long horizontal drain. Numerical simulation revealed that gravity drainage, as opposed to hydraulic gradients in the water phase, is the dominant recovery mechanism at this site. This stems from the relatively high density and the viscosity of the DNAPL, and the relatively low permeability of the formation deposits. The use of pulsed pumping is shown to reduce the volume of contaminated ground water recovered from the 9-drain system, without significant reduction of the total volume of DNAPL recovered.
2001-05-01T07:00:00Z
article
https://ir.lib.uwo.ca/civilpub/14
http://www3.interscience.wiley.com/journal/119930535/abstract
Civil and Environmental Engineering Publications
Scholarship@Western
DNAPL
DNAPL pool
ground water
DNAPL recovery
DNAPL stabilization
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1014
2011-08-31T00:24:21Z
publication:civil
publication:faculties
publication:civilpub
Systems Approach to Management of Disasters: Methods and Applications
Simonović, Slobodan P.
The main goal of this text is to introduce the systems approach to disasters management community as an alternative approach that can provide support for interdisciplinary activities involved in the management of disasters. The systems approach draws on the fields of operations research and economics to create skills in solving complex management problems.
2011-01-01T08:00:00Z
book
https://ir.lib.uwo.ca/civilpub/15
info:doi/10.1002/9780470890363
http://dx.doi.org/10.1002/9780470890363
Civil and Environmental Engineering Publications
Scholarship@Western
Systems Approach
Disaster Management
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1017
2016-01-07T01:42:59Z
publication:civil
publication:faculties
publication:civilpub
Remediation of Trichloroethylene-Contaminated Soils by STAR Technology using Vegetable Oil Smoldering
Gerhard, Jason
Salmana, Madiha
Major, David W.
Pironi, Paolo
Hadden, Rory
Self-sustaining treatment for active remediation (STAR) is an innovative soil remediation approach based on smoldering combustion that has been demonstrated to effectively destroy complex hydrocarbon nonaqueous phase liquids (NAPLs) with minimal energy input. This is the first study to explore the smoldering remediation of sand contaminated by a volatile NAPL (trichloroethylene, TCE) and the first to consider utilizing vegetable oil as supplemental fuel for STAR. Thirty laboratory-scale experiments were conducted to evaluate the relationship between key outcomes (TCE destruction, rate of remediation) to initial conditions (vegetable oil type, oil: TCE mass ratio, neat versus emulsified oils). Several vegetable oils and emulsified vegetable oil formulations were shown to support remediation of TCE via self-sustaining smoldering. A minimum concentration of 14,000 mg/kg canola oil was found to treat sand exhibiting up to 80,000 mg/kg TCE. On average, 75% of the TCE mass was removed due to volatilization. This proof-of-concept study suggests that injection and smoldering of vegetable oil may provide a new alternative for driving volatile contaminants to traditional vapour extraction systems without supplying substantial external energy.
2015-03-21T07:00:00Z
article
application/pdf
https://ir.lib.uwo.ca/civilpub/16
info:doi/10.1016/j.jhazmat.2014.11.042
http://dx.doi.org/10.1016/j.jhazmat.2014.11.042
http://creativecommons.org/licenses/by-nc-nd/4.0/
Civil and Environmental Engineering Publications
Scholarship@Western
Smoldering; Thermal; Remediation; NAPL; VOCs; Vegetable oil
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1018
2016-01-06T22:33:52Z
publication:civil
publication:faculties
publication:civilpub
Smoldering Remediation of Coal-Tar-Contaminated Soil: Pilot Field Tests of STAR
Gerhard, Jason
Scholes, Grant C.
Grant, Gavin P.
Major, David W.
Vidumsky, John E.
Switzer, Christine
Torero, Jose L.
Self-sustaining treatment for active remediation (STAR) is an emerging, smoldering-based technology for nonaqueous-phase liquid (NAPL) remediation. This work presents the first in situ field evaluation of STAR. Pilot field tests were performed at 3.0 m (shallow test) and 7.9 m (deep test) below ground surface within distinct lithological units contaminated with coal tar at a former industrial facility. Self-sustained smoldering (i.e., after the in-well ignition heater was terminated) was demonstrated below the water table for the first time. The outward propagation of a NAPL smoldering front was mapped, and the NAPL destruction rate was quantified in real time. A total of 3700 kg of coal tar over 12 days in the shallow test and 860 kg over 11 days in the deep test was destroyed; less than 2% of total mass removed was volatilized. Self-sustaining propagation was relatively uniform radially outward in the deep test, achieving a radius of influence of 3.7 m; strong permeability contrasts and installed barriers influenced the front propagation geometry in the shallow test. Reductions in soil hydrocarbon concentrations of 99.3% and 97.3% were achieved in the shallow and deep tests, respectively. Overall, this provides the first field evaluation of STAR and demonstrates that it is effective in situ and under a variety of conditions and provides the information necessary for designing the full-scale site treatment.
2015-11-02T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/17
info:doi/10.1021/acs.est.5b03177
Civil and Environmental Engineering Publications
Scholarship@Western
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1019
2016-01-06T22:55:24Z
publication:civil
publication:faculties
publication:civilpub
Self-sustaining Smouldering Combustion of Coal Tar for the Remediation of Contaminated Sand: Two–Dimensional Experiments and Computational Simulations
Gerhard, Jason
Hasan, Tanzeer
Hadden, Rory
Rein, Guillermo
This study presents the development and validation of a computational model which simulates the propagation of a smouldering front through a porous medium against unique experiments in coal tar and sand. The model couples a multiphase flow solver in porous media with a perimeter expansion module based on Huygens principle to predict the spread. A suite of two-dimensional experiments using coal tar- contaminated sand were conducted to explore the time-dependent vertical and lateral smouldering front 6 propagation rates and final extent of remediation as a function of air injection rate. A thermal severity analysis revealed, for the first time, the temperature-time relationship indicative of coal tar combustion. The model, calibrated to the base case experiment, then correctly predicts the remaining experiments. This work provides further confidence in a model for predicting smouldering, which eventually is expected to be useful for designing soil remediation schemes for a novel technology based upon smouldering destruction of organic contaminants in soil.
2015-06-15T07:00:00Z
article
application/pdf
https://ir.lib.uwo.ca/civilpub/18
info:doi/10.1016/j.fuel.2015.02.014
http://dx.doi.org/10.1016/j.fuel.2015.02.014
Civil and Environmental Engineering Publications
Scholarship@Western
smouldering
remediation
multiple dimensions
modelling
thermal severity
Civil and Environmental Engineering
oai:ir.lib.uwo.ca:civilpub-1021
2019-02-13T18:04:25Z
publication:civil
publication:rwkex_researcharticles
publication:faculties
publication:rwkex
publication:civilpub
Slowdown of surface diffusion during early stages of bacterial colonization
Vourc'h, T.
Peerhossaini, H.
Leopoldes, J.
Mejean, A.
Chauvat, F.
Cassier-Chauvat, C.
We study the surface diffusion of the model cyanobacterium Synechocystis sp. PCC6803 during the incipient stages of cell contact with a glass surface in the dilute regime. We observe a twitching motility with alternating immobile tumble and mobile run periods, resulting in a normal diffusion described by a continuous-time random walk with a coefficient of diffusion D. Surprisingly, D is found to decrease with time down to a plateau. This is observed only when the cyanobacterial cells are able to produce released extracellular polysaccharides, as shown by a comparative study between the wild-type strain and various polysaccharides-depleted mutants. The analysis of the trajectories taken by the bacterial cells shows that the temporal characteristics of their intermittent motion depend on the instantaneous fraction of visited sites during diffusion. This describes quantitatively the time dependence of D, related to the progressive surface coverage by the polysaccharides. The observed slowdown of the surface diffusion may constitute a basic precursor mechanism for microcolony formation and provides clues for controlling biofilm formation.
2018-01-01T08:00:00Z
article
application/pdf
https://ir.lib.uwo.ca/civilpub/19
info:doi/10.1103/PhysRevE.97.032407
https://ir.lib.uwo.ca/context/civilpub/article/1021/viewcontent/Slowdown_of_surface_diffusion_during_early_stages_of_bacterial_colonization.pdf
Civil and Environmental Engineering Publications
Scholarship@Western
MOTILITY
CHEMOTAXIS
BIOFILMS
EXOPOLYSACCHARIDES
PHOTOTAXIS
MICROSCOPY
MECHANISM
PCC6803
SLIME
PILI
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1025
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Micro-mixing measurement by chemical probe in homogeneous and isotropic turbulence
Lemenand, T.
Della Valle, D.
Habchi, C.
Peerhossaini, H.
The chemical probe is commonly used to evaluate the performance of chemical reactors. By a localized injection of chemical reagents, it is possible to measure the local micro-mixing, which is readily related to the selectivity of chemical reactions, since mixing at the molecular scale is the limiting factor for a Wide range of chemical systems. The raw result of the chemical-probe method is a segregation index that allows comparison of different situations (various locations in the reactor, various Reynolds numbers, various geometries, etc.). Beyond the qualitative assessment provided by this segregation index, it is possible to obtain the intrinsic micro-mixing time by means of a micro-mixing model, describing the temporal evolution of a chemical reaction whose rate is governed by the micro-mixing. Here a key step is the choice of micro-mixing model. Several micro-mixing models available in the literature have been used in some specific cases without evaluating their appropriateness for the problem in hand. The main difficulty in this evaluation is that the real flows often do not fully satisfy the basic model assumptions, in particular the condition of homogeneous and isotropic turbulence (HIT). The present work aims at assessing the validity of a micro-mixing model under "ideal" experimental conditions, i.e. HIT with no mean flow, to avoid the bias due to the flow gradients. The HIT is obtained here by a system of oscillating grids placed in a vessel. The chemical probe measurements carried out by the iodide/iodate reaction system are applied to the two most commonly used phenomenological models in the literature: the IEM (Interaction by Exchange with the Mean) and the EDD (Engulfment, Deformation and Diffusion) models. The benchmark for the micro-mixing models is based on comparison of the local turbulent kinetic energy (TKE) dissipation rate both drawn from the micro-mixing time by the theoretical model of Baldyga and the reference direct experimental determination by laser Doppler velocimetry measurements. It is shown that the engulfment model EDD seems the more appropriate to analyze the chemical data and provide a quantitative characterization of micro-mixing. (C) 2016 Elsevier B.V. All rights reserved.
2017-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/23
info:doi/10.1016/j.cej.2016.12.001
Civil and Environmental Engineering Publications
Scholarship@Western
GRID-GENERATED TURBULENCE
MULTIFUNCTIONAL HEAT-EXCHANGERS
IODATE REACTION SYSTEM
MICROMIXING EFFICIENCY
DENSITY INTERFACES
ENERGY-DISSIPATION
STATIC MIXERS
REACTORS
MODEL
PRECIPITATION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1027
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Heat transfer at the grinding interface between glass plate and sintered diamond wheel
Moussa, Tala
Garnier, Bertrand
Pelay, Ugo
Favennec, Yann
Peerhossaini, Hassan
Heat transfer analysis is of great importance for temperature prediction during grinding. Indeed the grinding parameters have to be adjusted to accelerate the manufacturing process while minimizing thermal damage to the workpiece. The temperature survey is especially critical for the grinding of glass material because of its low thermal conductivity inducing high temperature rise. In our study, temperatures at different locations in the sintered diamond composites of the grinding wheel are measured using thermocouples and a radio transmission technique. The glass temperature is measured using thermocouple strips on both side of glass plate, the grinding wheel providing the electrical connection between them. Results during grinding with a 6500 rpm rotation velocity shows temperature lower than 80 degrees C inside the grinding wheel while temperature up to 900 degrees C is found on glass. An inverse approach is used to compute the wall heat flux and temperature at the wall of the grinding wheel using a 2D axisymmetric heat transfer model. A 1D non linear heat transfer model including conduction and radiation is used to obtain the wall heat flux of the glass material. Knowing temperatures and heat fluxes on both side of the interface, one deduces information on thermal contact resistance, generated heat flux and partition ratio. So, the heat generated by the grinding is estimated between 223 and 399 W depending on the grinding process conditions and is localized on the glass side of the interface. The thermal contact resistance at the glass/sintered diamond composites figures out to be very high with a value greater than 3.8 10(-3) m(2)K W-1. (C) 2016 Elsevier Masson SAS. All rights reserved.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/25
info:doi/10.1016/j.ijthermalsci.2016.03.027
Civil and Environmental Engineering Publications
Scholarship@Western
TEMPERATURE-MEASUREMENT
SLIDING CONTACTS
FLUX
COOLANT
MODEL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1030
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Effect of air temperature non-uniformity on water-air heat exchanger thermal performance - Toward innovative control approach for energy consumption reduction
Ramadan, M.
Khaled, M.
El Hage, H.
Harambat, F.
Peerhossaini, H.
Parametric numerical analysis that explores the relation between the non-uniformity of air temperature distribution upstream of a heat exchanger and its thermal performance is performed. The obtained numerical results are employed toward the optimization of water-air heat exchanger thermal performance. Furthermore, the numerical results lay out the foundation to develop an innovative control approach for monitoring the airflow upstream of a cross-flow water-air heat exchanger that lead to the optimization of its thermal performance and energy consumption. Consequently, an in-house computational code is established to evaluate the aforementioned thermal performance based on known parameters; namely, distribution of upstream velocity and temperature of an air-liquid heat exchanger, the flow rate of heat exchanger liquid, in addition to the inlet liquid temperature. It was observed that non-uniformities in air temperature can, depending on the configuration, increase or decrease the thermal performance of a heat exchanger up to 5%. Additionally, controlling air temperature non-uniformities, the fuel consumption and carbon dioxide emission can be reduced by up to 0.97 kg (1.34 L) and 3.17 kg respectively for a vehicle running three hours per day. (C) 2016 Elsevier Ltd. All rights reserved.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/28
info:doi/10.1016/j.apenergy.2016.04.076
Civil and Environmental Engineering Publications
Scholarship@Western
FLOW MALDISTRIBUTION
INLET TEMPERATURES
FIN
OPTIMIZATION
SIMULATION
SYSTEMS
DESIGN
CONDUCTION
PARALLEL
BAFFLES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1037
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Analysis and modeling of the thermal soak phase of a vehicle - Temperature and heat flux measurements
Khaled, M.
Elrab, M. G.
Habchi, C.
Al Shaer, A.
Elmarakbi, A.
Harambat, F.
Peerhossaini, H.
The thermal soak phase of a vehicle results from driving the vehicle at high load followed by shutting off the engine. The present work deals with the analysis and modeling of the thermal soak phase of a vehicle through temperature and heat flux measurements. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France. The underhood is instrumented by alsmot 120 surface and air thermocouples and 20 fluxmeters. Measurements are performed for three thermal functioning conditions, with the engine in operation and the front wheels positioned on the test facility with power-absorption controlled rollers. It was found that in thermal soak the temperature of certain components can increase by almost 80A degrees C (pre-catalyst) and that of air zones by alsmot 40A degrees C (crawl area). These components correspond to areas that heat up after stopping the engine for 3 to 24 minutes, depending on their position in the underhood and on the thermal operating point considered.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/35
info:doi/10.1007/s12239-015-0024-3
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1041
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Energy Management in Car Underhood Compartment-Temperature and Heat Flux Analysis of Car Inclination Effects
Khaled, Mahmoud
El Hage, Hisham
Harambat, Fabien
Peerhossaini, Hassan
It has been shown by the authors that car inclination influences the temperatures of different underhood components. Here these effects are analyzed by heat-flux measurements. The results of underhood temperature and heat-flux measurements carried out on a passenger vehicle in wind-tunnel S4 of Saint-Cyr l'Ecole are presented. The underhood compartment of the vehicle is instrumented with 40 surface and air thermocouples and 20 flux meters of normal gradient. Experiments are performed with a specific technique for separate measurement of convective and radiative heat fluxes. Three car position configurations are tested: flat, uphill, and downhill positions. Measurements are made for three different thermal functioning modes. Fluxmetric analysis based on overall heat flux as well as on separate convective and radiative heat fluxes is reported here in order to establish the effects and variation tendencies of car inclination on the temperature-heat flux pair. For most of the tested positions in the underhood top region, the car inclination improves convective heat transfer and penalizes radiative heat transfer. The reduction in radiative heat transfer dominates the convective heat-transfer improvement, resulting in augmentation of the overall heat flux as well as the temperature.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/39
info:doi/10.1080/01457632.2014.906283
Civil and Environmental Engineering Publications
Scholarship@Western
DIESEL-ENGINE
SYSTEM
CONSUMPTION
COMBUSTION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1024
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Temperature measurement of flat glass edge during grinding and effect of wheel and workpiece speeds
Moussa, Tala
Garnier, Bertrand
Peerhossaini, Hassan
Flat glass temperature at the vicinity of the grinding wheel during grinding can become very high and reach that of the glass transition (typically around 550-600 degrees C). In such cases, the mechanical strength of glass is greatly affected and the grinding process cannot be carried out properly. Hence, thermal phenomena must be managed by adjusting the machining parameters to avoid overheating. For this purpose, it is very important to be able to measure the glass temperature, especially at the grinding interface. However, measuring the interfacial glass temperature is difficult and none of the existing methods for metal grinding is adequate for glass grinding. This work shows a novel temperature method that uses constantan and copper strips on both sides of the glass plates; thermoelectric contact being provided by the metallic binder of diamond particles in the grinding wheel. This new technique allows the measurement of the glass edge temperature during the wheel displacement around the glass plate. The experimental results show an average glass edge temperature between 300 and 600 degrees C depending on the value of the machining parameters such as work speed, wheel speed, depth of cut and water coolant flow rate. As this new thermal instrumentation is rather intrusive, glass temperature biases were analysed using a 3D heat transfer model with a moving source. Model computations performed using finite elements show that the temperature biases are less than 70 degrees C, which is smaller than the standard deviation of the glass edge temperatures measured during grinding.
2017-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/22
info:doi/10.1088/1361-6501/aa65a7
Civil and Environmental Engineering Publications
Scholarship@Western
HIGH-EFFICIENCY
HEAT-TRANSFER
SUBSURFACE
DAMAGE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1026
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Turbulence statistics downstream of a vorticity generator at low Reynolds numbers
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Vortex generators (VGs) are inserted in turbulent pipe flows in order to improve mixing and heat and mass transfer while a moderate pressure drop is maintained. The purpose of the present study is to contribute to the elaboration of scaling laws for the turbulence decay downstream a row of VGs. This knowledge will help in the design of such systems, especially for optimal geometry and spacing of the VG. The experimental study is carried out using laser Doppler anemometry at different locations downstream of the row of VGs so as to probe the streamwise velocity field. The Taylor microscale Reynolds number Re. ranges between 15 and 80 so that, for the lowest flow rates, fully developed turbulence conditions are not fulfilled. Comparison of the integral length scale to data in the open literature shows that the conventional scaling laws at the dissipative scale are fairly assessed. It is shown that the turbulence macroscale increases in the streamwise direction and is scaled by the VG dimensions. The normalized turbulent energy dissipation rate has values between 0.5 and 2.8, with -1 power-law decay as a function of the Taylor microscale Reynolds number. This observation is consistent with previous findings using direct numerical simulations (DNS). The streamwise variation of the turbulence energy dissipation rate shows an exponential decay; it reaches an asymptotic value after a distance of about 6 times the VG height. Published by AIP Publishing.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/24
info:doi/10.1063/1.4964924
Civil and Environmental Engineering Publications
Scholarship@Western
ENERGY-DISSIPATION RATE
STATIC MIXERS
HEAT-TRANSFER
ISOTROPIC TURBULENCE
LENGTH SCALE
FLOW
TRANSITION
VELOCITY
CROSS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1023
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Some observations on the spatiotemporal orbits structure and heat transfer enhancement in pulsating flow
Habibi, Zahra
Karami, Mohammad
Jarrahi, Mojtaba
Shirani, Ebrahim
Peerhossaini, Hassan
We describe in this work a numerical simulation of chaotic heat transfer by laminar flow in a twisted pipe that consists of three bends. Observations on the secondary flow topology changed by the variation of Reynolds number and tube wall temperature as well as their coincidence with heat transfer enhancement are discussed. Both steady and pulsating flows with constant wall temperature are considered. Numerical simulations are performed for Reynolds numbers range 300 <= Re <=. 1000, velocity amplitude ratios (the ratio of the peak oscillatory velocity component to the mean flow velocity) 1 <= beta <= 2, Womersley numbers 6 <= alpha <= 20, and wall temperatures 310 <= T-w(K) <= 360. It is observed that the variation of the number of elliptic orbits (cells) and the area covered by cell centers in the pipe cross-section are two crucial factors in heat transfer enhancement. When the Reynolds number increases in the steady and pulsating flows, the number of elliptic orbits in the secondary flow patterns is increased and heat transfer is enhanced. However, heating uniformity is degraded with increasing Reynolds number that results in the reduction of heat exchanger performance. For the pulsating flows, small and moderate values of Womersley numbers (6 <= alpha <= 12) and high values of velocity amplitude ratios (beta > 1) provide a more complex secondary flow and hence a better heat transfer. Pulsation energy consumption is higher than the energy needed for increasing Reynolds number of the steady flow to match the same heat transfer enhancement. However, a better heating uniformity is obtained in the pulsating flow, which is not the case in the steady flow.
2018-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/21
info:doi/10.1016/j.ijthermalsci.2017.12.006
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION
TURBULENT-FLOW
LAMINAR-FLOW
PIPE
EXCHANGER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1028
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Parametric Analysis of Heat Exchanger Thermal Performance in Complex Geometries-Effect of Air Velocity and Water Flow Distributions
Khaled, Mahmoud
Ramadan, Mohamad
Shaito, Ali
El Hage, Hicham
Harambat, Fabien
Peerhossaini, Hassan
The thermal performance of automotive heat exchangers is greatly affected by the relationship that binds the nonuniformities in flow velocity and the distribution of upstream temperatures. Consequently, an in-house two-dimensional code is established to evaluate the thermal performance based on known parameters, namely, distribution of upstream velocity of an air-liquid heat exchanger, the flow rate of heat exchanger liquid, and the inlet air and liquid temperatures. A parametric research study is then performed to confirm the relation between the thermal performance of the heat exchanger and these different parameters. It was observed that nonuniformities in air velocity and water flow distributions decrease the thermal performance of a heat exchanger by up to 33 and 42%, respectively.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/26
info:doi/10.1080/01457632.2015.1104166
Civil and Environmental Engineering Publications
Scholarship@Western
LOUVERED FIN
MALDISTRIBUTION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1022
2019-02-13T18:11:15Z
publication:civil
publication:faculties
publication:civilpub
Vorticity and convective heat transfer downstream of a vortex generator
Lemenand, Thierry
Habchi, Charbel
Della Valle, Dominique
Peerhossaini, Hassan
Vorticity generation has been identified, since the 80's, as an efficient means for enhancing heat transfer; the mean radial velocity component due to the induced flow pattern contributes to the heat removal. In the present work, momentum and heat transfer are studied in a test section designed to mimic the industrial HEV (High-Efficiency Vorticity) mixer. It consists of a basic configuration with a unique vorticity generator inserted on the bottom wall of a heated straight channel. The aim of this work is to analyze to which extend the convective heat transfer is correlated to the vorticity, as it is presumed to cause the intensification. In this case, the driving vorticity is the streamwise vorticity flux Omega, and the heat transfer is characterized by the Nusselt number Nu, both quantities being spanwise averaged. The study is mainly numerical; we have used the previous PIV measurements and DNS data from the open literature to validate the numerical simulations. It is shown that there exists a strong correlation between the vorticity flux and Nusselt number close to the vortex generator. However, the axial variation diverges for these quantities when moving downstream. The Nusselt number presents a sharp peak over the VG and decreases nearly to its basic level just behind the VG, while the vortex persists far downstream from the tab and relaxes very slowly. Heat transfer intensification at the Nusselt peak is about 100%, and reduces to about 6% downstream of the VG, the intensity of the vorticity momentum being decreased only to about 50% of its peak value at the test section outlet.
2018-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/20
info:doi/10.1016/j.ijthermalsci.2017.11.021
https://doi.org/10.1016/j.ijthermalsci.2017.11.021
Civil and Environmental Engineering Publications
Scholarship@Western
TRANSFER ENHANCEMENT
STREAMWISE VORTICITY
CHAOTIC ADVECTION
TURBULENT-FLOW
MASS-TRANSFER
CHANNEL FLOW
EXCHANGER
WALL
MECHANISMS
SEPARATION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1031
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Experimental study of the thermal performance of chaotic geometries for their use in PEM fuel cells
Castelain, Cathy
Lasbet, Yahia
Auvity, Bruno
Peerhossaini, Hassan
In order to improve the thermal performance of heat exchangers used in the bipolar plates of PEM fuel cells, we suggest replacing the networks of straight channels by geometries generating chaotic flows. In transport applications, high heat densities are generated because of the combined high heat fluxes and the imposed compactness of heat exchangers. Moreover, the convective regime in the cooling channels is laminar and the channel network has to be as thin as possible to limit the electrical resistance through the bipolar plates. In such extreme conditions, the generation of spatial chaos by geometrical perturbation in the heat exchanger is a relevant way to intensify heat transfer. In this paper, an experimental study is presented for two chaotic advection geometries and a straight tube. A specialized test bench was designed and built. The channels were placed in a counterflow heat exchanger with a laminar flow in the center and a turbulent flow in the annulus. Heat exchange was carefully analyzed to obtain the convective heat transfer coefficient for each channel. (C) 2015 Elsevier Masson SAS. All rights reserved.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/29
info:doi/10.1016/j.ijthermalsci.2015.10.033
Civil and Environmental Engineering Publications
Scholarship@Western
HEAT-TRANSFER
MICROCHANNEL NETS
BIPOLAR PLATES
PRESSURE-DROP
ADVECTION
PIPE
EXCHANGER
FLOW
MANAGEMENT
DESIGNS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1032
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
EFFECTS OF SHEAR STRESS ON THE GROWTH RATE OF MICRO-ORGANISMS IN AGITATED REACTORS
Fadlallah, Hadi
Jarrahi, Mojtaba
Herbert, Eric
Ferrari, Roselyne
Mejean, Annick
Peerhossaini, Hassan
The effects of hydrodynamic shear stress on the growth rate of cyanobacteria Synechocystis sp. and Chlamydomonas reinhardtii microalgae cells were studied in agitated photobioreactors, since they have different motility rates and sizes. An experimental setup was designed and constructed to monitor the growth rate of the micro-organisms versus the shear rate; experiments were carried out in a well controlled environment, under constant atmospheric pressure and 20 degrees C temperature. Digitally controlled magnetic agitator-photobioreactors were placed inside a closed chamber with air flow for 4 weeks, under a uniform full-time light intensity provided by two 6-watt white fluorescent light sources. To study the effects of shear stress produced by mechanical agitation on the growth rate of a micro-organism, different agitation frequencies were tested. All reactors were filled with 150 ml of culture medium and micro-organism suspension, with initial dilution factors (ml(suspenion)/Ml(total) (volume)) of 1/30 and 1/300 for Synechocystis and C. reinhardtii respectively. The vessels were placed on different agitating systems at the desired agitator rotation speed, and were sealed with a cotton membrane from the top in order to permit air exchange with the external environment. The micro-organisms' growth was monitored daily by measuring the optical density of the suspensions using a spectrophotometer and was' hen correlated with the cellular concentration, which was measured in turn using a microscopic cell counter. Throughout the experiments pH levels and temperature were measured regularly and adjusted to 7 and 20 C respectively in order to maintain the photosynthetic activity of the species. In addition, to measure the shear stress inside the agitated reactors, a mathematical model was derived to determine the global shear stress magnitude. To determine the local shear stress distribution, the velocity field in the reactor was measured for different agitation frequencies using PIV. Different zones of high and low shear stress were identified. The results showed that the growth rate is independent of the shear stress magnitude for Synechocystis; Synechocystis showed strong resistance, unlike C. reinhardtii, which showed linear dependence of growth rate and shear stress.
2016-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/30
info:doi/10.1115/FEDSM2016-7590
Civil and Environmental Engineering Publications
Scholarship@Western
PHAEODACTYLUM-TRICORNUTUM
PORPHYRIDIUM-CRUENTUM
HYDRODYNAMIC STRESS
MICROALGAE
PHOTOBIOREACTORS
TOLERANCE
BIODIESEL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1033
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
MOTION OF ACTIVE FLUIDS: DIFFUSION DYNAMICS OF CYANOBACTERIA
Vourc'h, Thomas
Leopoldes, Julien
Mejean, Annick
Peerhossaini, Hassan
Cyanobacteria are photosynthetic micro-organisms colonizing all aquatic and terrestrial environments. The motility of such living micro-organisms should make their diffusion distinct from typical Brownian motion. This diffusion can be investigated in terms of global behavior (Fickian or not) and in terms of displacement probabilities, which provide more detail about the motility process. Using cyanobacterium Synechocystis sp. PCC 6803 as the model micro-organism, we carry out time-lapse video microscopy to track and analyze the bacteria's trajectories, from which we compute the mean squared displacement (MSD) and the distribution function of displacement probabilities. We find that the motility of Synechocystis sp. PCC 6803 is intermittent: high-motility "run" phases are separated by low motility "tumble" phases corresponding to trapped states. However, this intermittent motility leads to a Fickian diffusive behavior, as shown by the evolution of the MSD with time.
2016-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/31
info:doi/10.1115/FEDSM2016-7526
Civil and Environmental Engineering Publications
Scholarship@Western
FLOW
PHOTOTAXIS
MOTILITY
WALL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1035
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Numerical and experimental hydrodynamic study of a coolant distributor for grinding applications
Moussa, Tala
Della Valle, Dominique
Garnier, Bertrand
Peerhossaini, Hassan
In grinding, the high frictional energy is converted into heat, which may cause thermal damage and degradation of the wheel and the workpiece. Unwanted thermal effects must thus be reduced, often by external cooling using a curved-duct coolant distributor to match the wheel geometry. The performance of such a system depends strongly on the impinging jet flow properties to ensure efficient sprinkling of the hot spots. The fluid distributor, placed above the workpiece, is pierced with a certain number of identical nozzle fittings, providing multiple jets at the outlet of the nozzles. These jets sprinkle the solids over a given zone and remove the heat by convective transfer. The cooling is hence dependent on the flow structure, meaning the jet diameters, trajectories and velocities, determined up-flow by the distributor design. The present study is devoted to the hydrodynamics aspects of the fluid distributor, aiming to determine the flow-rate distribution at the different orifices and the flow-rate-pressure relationship, for a variety of nozzle diameters and feeding flow rates, under isothermal conditions. A simple hydraulic balance in the device was not able to predict with sufficient accuracy the actual measurements, even when the Venturi effect was accounted for. This discrepancy is due to the curvature of the distributor, inducing secondary flows in interaction with the nozzle outlets, which leads to a rather complex flow pattern. To overcome this issue, a computational fluid dynamics (CFD) tool was used and compared with in situ experiments - global flow rate and pressure measurements were additionally taken with particle image velocimetry (PIV) to gain insight into the local structure. Simulations were performed with a 3D turbulence model for Reynolds numbers up to 100,000. This model provides an efficient tool for coupling with the thermal study at a later step, allowing global sizing and energetic optimization of the grinding process.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/33
info:doi/10.1080/19942060.2015.1102170
Civil and Environmental Engineering Publications
Scholarship@Western
HEAT-TRANSFER ENHANCEMENT
GORTLER INSTABILITY
U-BEND
JETS
FLOW
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1029
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
EXPERIMENTAL STUDY OF THE FLOW INDUCED BY A VEHICLE FAN AND THE EFFECT OF ENGINE BLOCKAGE IN A SIMPLIFIED MODEL
Khaled, M.
El Rab, M. Gad
Hachem, F.
Elhage, H.
Elmarakbi, A.
Harambat, F.
Peerhossaini, H.
Fans are often tested without downstream blockage and, thus, the performance is considerably different when the fan is mounted in a vehicle as part of a cooling system and where high blockage effect is present downstream. The aim of the present work is to analyze by laser Doppler velocimetry LDV measurements the topology of the flow induced by a fan incorporated in a simplified underhood model reproducing engine blockage and to study the blockage effect of the engine positioning on the flow induced by the fan. The distance between the fan and the engine block affects the mean flow axial velocity U. The vertical velocity component W is greatly influenced by the variation of the distance between the fan and the engine block, both in magnitude and topology.
2016-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/27
info:doi/10.1007/s12239-016-0061-6
Civil and Environmental Engineering Publications
Scholarship@Western
COOLING SYSTEM
LIFE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1038
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Modeling Open-Flow Steam Reforming of Methanol over Cu/ZnO/Al2O3 Catalyst in an Axisymmetric Reactor
Pacheco, L.
Della-Valle, D.
Le Corre, O.
Habchi, C.
Lemenand, T.
Peerhossaini, H.
This paper describes a CFD study of the steam-reforming process (SRP) of methanol in a short pseudo-contact time reactor of fixed bed type, in axi-symmetric conditions. The SRP is important sake for hydrogen production, and the design /scale-up/control of the industrial processes in the future are supported by a reliable knowledge and prediction of the catalytic reaction. The difficulty of determining the reaction scheme and the associated constants is well-known, due to the necessity of identifying the reaction kinetics in purely chemical regime, meaning with a perfect homogeneity and flow independence. Practically these ideal conditions, albeit assumed, are not fulfilled so that the intrinsic chemical kinetics is not reached. For the case of SRP, we have attempted here to validate the Peppley's model by a numerical modelling reproducing exactly the local conditions in the experimental duct, accounting for gradients in the cross section. The numerical results show the same trends than the experimental one, but with a slight shift of 20% as a consequence of the reactor heterogeneity. This result seems acceptable to validate the use of the Peepley's model for further studies in other types of complex flow reactors.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/36
Civil and Environmental Engineering Publications
Scholarship@Western
COPPER-BASED CATALYSTS
HYDROGEN
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1036
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Experimental study of the turbulent field behind a perforated vortex generator
Habchi, C.
Lemenand, T.
Della Valle, D.
Al Shaer, A.
Peerhossaini, H.
The influence of the wake vortex arising behind a perforated tab on the mixing process in heat exchangers and chemical reactors is analyzed. The preliminary step of this study, i.e., investigation of the turbulent field generated by a single perforated tab, is presented here. For this aim, laser Doppler velocimetry measurements are conducted downstream from a perforated trapezoidal vortex generator placed in a wind tunnel. It is shown that two shear layers are generated by the tab. The first shear layer is located at the upper edge of the tab, and the other is ejected from the perforation edges. These shear layers are characterized by high turbulent kinetic energy levels, which are profitable for meso-mixing enhancement. Finally, a spectral study shows that the turbulent macro-scale is nearly the same for typical locations in the shear layers shed from the tab and perforation edges.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/34
info:doi/10.1134/S0021894415040045
Civil and Environmental Engineering Publications
Scholarship@Western
HEAT-TRANSFER
FLOW
TAB
STATISTICS
VORTICES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1034
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
HEAT TRANSFER ENHANCEMENT IN SPLIT AND RECOMBINE FLOW CONFIGURATIONS: A NUMERICAL AND EXPERIMENTAL STUDY
Jarrahi, Mojtaba
Thermeau, Jean-Pierre
Peerhossaini, Hassan
Heat transfer enhancement in laminar regime by split and recombine (SAR) mechanism, based on the baker's transformation, is investigated. Two different heat exchangers, called SARI and SAR2, are studied. Their geometries are inspired from the previous studies reported in the literature. The working fluid on both, shell and tube side, is water and the temperature on the shell side is kept constant. Experiments are carried out for the Reynolds number range 1001000, and provides a less uniform temperature field at the outlet.
2016-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/32
info:doi/10.1115/HT2016-7119
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION
COILED-TUBE
EXCHANGER
MIXER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1040
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mixing by Time-Dependent Orbits in Spatiotemporal Chaotic Advection
Karami, Mohammad
Shirani, Ebrahim
Jarrahi, Mojtaba
Peerhossaini, Hassan
The simultaneous effects of flow pulsation and geometrical perturbation on laminar mixing in curved ducts have been numerically studied by three different metrics: analysis of the secondary flow patterns, Lyapunov exponents and vorticity vector analysis. The mixer that creates the flow pulsation and geometrical perturbations in these simulations is a twisted duct consisting of three bends; the angle between the curvature planes of successive bends is 90 deg. Both steady and pulsating flows are considered. In the steady case, analysis of secondary flow patterns showed that homoclinic connections appear and become prominent at large Reynolds numbers. In the pulsatile flow, homoclinic and heteroclinic connections appear by increasing beta, the ratio of the peak oscillatory velocity component of the mean flow velocity. Moreover, sharp variations in the secondary flow structure are observed over an oscillation cycle for high values of beta. These variations are reduced and the homoclinic connections disappear at high Womersley numbers. We show that small and moderate values of the Womersley number ( 6 <= alpha <= 10) and high values of velocity amplitude ratio ( beta >= 2) provide a better mixing than that in the steady flow. These results correlate closely with those obtained using two other metrics, analysis of the Lyapunov exponents and vorticity vector. It is shown that the increase in the Lyapunov exponents, and thus mixing enhancement, is due to the formation of homoclinic and heteroclinic connections.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/38
info:doi/10.1115/1.4027588
Civil and Environmental Engineering Publications
Scholarship@Western
TWISTED DUCT FLOW
CURVED PIPE
VISCOUS-FLOW
HEAT-EXCHANGER
TRANSPORT
SYSTEMS
DESIGN
NUMBER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1042
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Review of underhood aerothermal management: Towards vehicle simplified models
Khaled, Mahmoud
Ramadan, Mohamad
El-Hage, Hicham
Elmarakbi, Ahmed
Harambat, Fabien
Peerhossaini, Hassan
This paper concentrates on the assessment of automobiles aerothermal management; namely, the consequence of the architectural arrangements of electrical and mechanical components on the aerothermal behavior in the underhood compartment. Consequently, it is natural to review the architectural arrangements of underhood components implemented by automotive companies such as Renault, Peugeot, Audi, BMW, Mercedes, Volvo, General Motors, Jaguar, Land Rover, Porsche, Nissan, Chrysler, Ford, Hyundai, Kia, and Toyota. Moreover, this study will evaluate the qualitative impact of each individual component on the aerothermal environment of the underhood. Furthermore, the study is determined to examine explicitly the components architectural arrangements' of underhood compartments and present simplified models of the compartments so that they can serve as aerothermal baseline models in the early stages of design. Hence, the different components in the underhand compartment are classified with respect to aerothermal orders of impact. Followed, two geometrical models, simple and advanced, are developed based on the impact orders. These models serve for future aerothermal studies (analytical, numerical and experimental). Finally, a simplified vehicle model is designed and implemented as underhood compartment model. The structurally simplified model is already utilized in experiments and can be used afterward in both numerical and experimental analyses. (C) 2014 Elsevier Ltd. All rights reserved.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/40
info:doi/10.1016/j.applthermaleng.2014.08.037
Civil and Environmental Engineering Publications
Scholarship@Western
AIR-FLOW
PERFORMANCE
ENGINE
SYSTEMS
TEMPERATURE
COMPARTMENT
COMBUSTION
SIMULATION
PARAMETERS
EFFICIENCY
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1039
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Low frequency vibration induced streaming in a Hele-Shaw cell
Costalonga, M.
Brunet, P.
Peerhossaini, H.
When an acoustic wave propagates in a fluid, it can generate a second order flow whose characteristic time is much longer than the period of the wave. Within a range of frequency between ten and several hundred Hz, a relatively simple and versatile way to generate streaming flow is to put a vibrating object in the fluid. The flow develops vortices in the viscous boundary layer located in the vicinity of the source of vibrations, leading in turn to an outer irrotational streaming called Rayleigh streaming. Because the flow originates from non-linear time-irreversible terms of the Navier-Stokes equation, this phenomenon can be used to generate efficient mixing at low Reynolds number, for instance in confined geometries. Here, we report on an experimental study of such streaming flow induced by a vibrating beam in a Hele-Shaw cell of 2 mm span using long exposure flow visualization and particle-image velocimetry measurements. Our study focuses especially on the effects of forcing frequency and amplitude on flow dynamics. It is shown that some features of this flow can be predicted by simple scaling arguments and that this vibration-induced streaming facilitates the generation of vortices. (C) 2015 AIP Publishing LLC.
2015-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/37
info:doi/10.1063/1.4905031
Civil and Environmental Engineering Publications
Scholarship@Western
OSCILLATING CIRCULAR-CYLINDER
KEULEGAN-CARPENTER NUMBERS
FLOW
MICROFLUIDICS
BOUNDARY
WAVE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1043
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Flow Pulsation and Geometry Effects on Mixing of Two Miscible Fluids in Microchannels
Ammar, Houssein
el Moctar, Ahmed Ould
Garnier, Bertrand
Peerhossaini, Hassan
Many microfluidic applications involve chemical reactions. Most often, the flow is predominantly laminar, and without active or passive mixing enhancement the reaction time can be extremely long compared to the residence time. In this work we demonstrate the merits of the combination of flow pulsation and geometrical characteristics in enhancing mixing efficiency in microchannels. Mixing was studied by introducing a mixing index based on the gray level observed in a heterogeneous flow of pure water and water colored by rhodamine B. The effects of the injection geometry at the microchannel inlet and the use of pulsed flows with average Reynolds numbers between 0.8 and 2 were studied experimentally and numerically. It appeared that the mixing index increases with the nondimensional residence time (tau), which is inversely proportional to the Reynolds number. In addition, we show that the mixing efficiency depends strongly on the geometry of the intersection between the two fluids. Better mixing was achieved with sharp corners (arrowhead and T intersections) in all cases investigated. In pulsed flow, the mixing efficiency is shown to depend strongly on the ratio (beta) between the peak amplitude and the mean flow rate. Optimal conditions for mixing in the microchannels are summarized as a function of Reynolds number Re, the ratio beta, and the geometries.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/41
info:doi/10.1115/1.4027550
Civil and Environmental Engineering Publications
Scholarship@Western
INTERDIGITAL MICROMIXERS
MASS-TRANSFER
MICRO-MIXER
ENHANCEMENT
PERFORMANCE
PARAMETERS
CATALYST
REACTORS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1044
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mixing performances of swirl flow and corrugated channel reactors
Ghanem, Akram
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Four different geometrical solutions for tubular reactors are compared for transfer intensification in fluid processes: (1) a compact multi-tube with helical screw-tape inserts, (2) a plain corrugated channel with a smooth bend curvature, called "wavy channel", (3) a plain corrugated channel with a herringbone pattern, called "zigzag channel", and (4) a plain straight pipe serving as the reference case. The single-phase mixing abilities of these four devices are compared by the chemical probe method (Villermaux/Dushman iodide/iodate system) for a range of main-flow Reynolds numbers between 100 and 4000. The chemical probe method is used here to investigate the global mixing time in the entire reactor volume, as deduced from the segregation index by a phenomenological model. Experimental results reveal better mixing performance and reduced energy expenditures in the helical-insert tube, in both the laminar and turbulent regimes. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/42
info:doi/10.1016/j.cherd.2014.01.014
Civil and Environmental Engineering Publications
Scholarship@Western
MULTIFUNCTIONAL HEAT-EXCHANGERS
ASSESSING MICROMIXING EFFICIENCY
COMPETING REACTION SYSTEM
CHAOTIC ADVECTION FLOW
STIRRED-TANK REACTORS
KENICS STATIC MIXER
2 IMMISCIBLE FLUIDS
GORTLER INSTABILITY
STREAMWISE VORTICITY
TRANSFER ENHANCEMENT
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1062
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Energy efficiency in process industry - High-efficiency vortex (HEV) multifunctional heat exchanger
Ghanem, Akram
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
In the process industry, vortex generators are being increasingly incorporated in modern multifunctional heat exchangers/reactors to enhance heat and mass transfer and thus increase energy efficiency. Longitudinal and transverse pressure-driven vortices and shear-instability-driven flow structures generated by flow separation behind the vortex generators play a crucial role in convective transport phenomena. The purpose of this work is to demonstrate experimentally the effects of hydrodynamics on the transfer processes accompanying such flows. The high-efficiency vortex (HEV) is an innovative static mixer and a low energy consumption heat exchanger designed to exploit these types of vortices. Heat transfer results obtained in turbulent flow with embedded vorticity in this multifunctional heat exchanger are compared with numerical results in the literature. Both numerical and experimental results confirm the high energy efficiency of the HEV static mixer flow. (C) 2012 Elsevier Ltd. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/60
info:doi/10.1016/j.renene.2012.09.024
Civil and Environmental Engineering Publications
Scholarship@Western
2 IMMISCIBLE FLUIDS
GORTLER INSTABILITY
TRANSFER ENHANCEMENT
LONGITUDINAL VORTICES
STREAMWISE VORTICITY
FLOW STRUCTURE
CHANNEL FLOW
MIXING TAB
TURBULENCE
AUGMENTATION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1045
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Leakage effects in car underhood aerothermal management: temperature and heat flux analysis
Khaled, Mahmoud
Habchi, Charbel
Harambat, Fabien
Elmarakbi, Ahmed
Peerhossaini, Hassan
Air leakage from the engine compartment of a vehicle comes mainly from the junctions of the vehicle hood and the front end grill, the vehicle wings, the optical and the windshield. The present paper studies the thermal impact of these air leakage zones on the components of the vehicle engine compartment through temperature and heat-flux measurements. The front wheels of the test vehicle are positioned on a dynamometer and driven by the vehicle engine. The engine compartment is instrumented with almost 100 surface and air thermocouples and 20 fluxmeters of normal gradients. Measurements were made for three different thermal operating points. Five leak-sealing configurations are studied.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/43
info:doi/0.1007/s00231-014-1347-8
Civil and Environmental Engineering Publications
Scholarship@Western
FUEL CONSUMPTION
COOLING SYSTEM
COMBUSTION
ENGINE
PERFORMANCE
MODEL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1049
2019-02-14T19:51:33Z
publication:civil
publication:faculties
publication:civilpub
Static mixers: Mechanisms, applications, and characterization methods - A review
Ghanem, Akram
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Static mixers and multifunctional heat exchangers/reactors (MHE/R) are qualified as efficient receptacles for processes including physical or chemical transformations accompanied by heat transfer due to their high productivity and reduced energy expenditures. The present work reviews recent conceptual and technological innovations in passive static mixers and continuous in-line reactors. Current industrial applications are discussed from a process intensification perspective, focusing on mixing and mass transfer performance. Typical experimental techniques employed to characterize and quantify the mixing process are explored. The work is complemented by a review of mixing fundamentals, knowledge of which allows the development of theoretical models crucial for the analysis of experimental data, like the chemical probe mixing assessment method. Considering the development of continuous flow equipment in numerous processes, advances in this field will certainly be of increasing interest to the scientific and industrial communities. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
2014-01-01T08:00:00Z
review
https://ir.lib.uwo.ca/civilpub/47
info:doi/10.1016/j.cherd.2013.07.013
https://doi.org/10.1016/j.cherd.2013.07.013
Civil and Environmental Engineering Publications
Scholarship@Western
STIRRED-TANK REACTORS
MULTIFUNCTIONAL HEAT-EXCHANGERS
ASSESSING MICROMIXING EFFICIENCY
COMPETING REACTION SYSTEM
CHAOTIC ADVECTION FLOW
IODATE REACTION SYSTEM
2 IMMISCIBLE FLUIDS
GORTLER INSTABILITY
CHEMICAL-REACTIONS
MOTIONLESS MIXERS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1050
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
OPTIMIZED CHAOTIC HEAT EXCHANGER CONFIGURATIONS FOR PROCESS INDUSTRY: A NUMERICAL STUDY
Ghanem, Akram
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
A numerical investigation of chaotic laminar flow and heat transfer in isothermal-wall square-channel configurations is presented. The computations, based on a finite-volume method with the SIMPLEC algorithm, are conducted in terms of Peclet numbers ranging from 7 to 7x10(5). The geometries, based on the split-and-recombine (SAR) principle, are first proposed for micromixing purposes, and are then optimized and scaled up to three-dimensional minichannels with 3-mm sides that are capable of handling industrial fluid manipulation processes. The aim is to assess the feasibility of this mass- and heat-transfer technique for out-of-laboratory commercial applications and to compare different configurations from a process intensification point of view. The effects of the geometry on heat transfer and flow characteristics are examined. Results show that the flux recombination phenomenon mimicking the baker's transform in the SAR-1 and SAR-2 configurations produces chaotic structures and promotes mass transfer. This phenomenon also accounts for higher convective heat transfer exemplified by increased values of the Nusselt number compared to the chaotic continuous-flow configuration and the baseline plain square-duct geometry. Energy expenditures are explored and the overall heat transfer enhancement factor for equal pumping power is calculated. The SAR-2 configuration reveals superior heat-transfer characteristics, enhancing the global gain by up to 17-fold over the plain duct heat exchanger.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/48
info:doi/10.1115/FEDSM2013-16115
Civil and Environmental Engineering Publications
Scholarship@Western
TRANSFER ENHANCEMENT
GORTLER INSTABILITY
ADVECTION FLOW
VORTICITY
NUMBERS
FLUIDS
MIXER
PIPE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1052
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
NUMERICAL SIMULATION OF THE INTERACTION BETWEEN FLUID FLOW AND ELASTIC FLAPS OSCILLATIONS
Habchi, Charbel
Russeil, Serge
Bougeard, Daniel
Harion, Jean-Luc
Menanteau, Sebastien
El Hage, Hisham
El Marakbi, Ahmed
Peerhossaini, Hassan
Several numerical methods have been developed recently to solve problems including the interaction between viscous fluid flow and elastic solid structures. In this work, an in-house partitioned numerical solver is developed by using the open source C++ library OpenFOAM. Finite volume method is used to discretize the fluid flow problem on a moving mesh in an Arbitrary Lagrangian-Eulerian formulation and by using an adaptive time step. The structural elastic deformation is analyzed in a Lagrangian formulation using the St. Venant-Kirchhoff constitutive law. The solid structure is discretized by the finite volume method in an iterative segregated approach. The automatic mesh motion solver is based on Laplace smoothing equation with variable mesh diffusion. The strong coupling between the segregated solvers and the equilibrium on the fluid-structure interface are achieved by using an iterative implicit fixed-point algorithm with dynamic Aitken's relaxation method. The solver is first validated on a benchmark largely used in the open literature. Then, a: more complex case is studied including two elastic flaps immersed in a pulsatile fluid flow. The present solver predicts accurately the interaction between the complex flow structures generated by the flaps and the effect of the flaps oscillations on each other.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/50
info:doi/10.1115/FEDSM2013-16352
Civil and Environmental Engineering Publications
Scholarship@Western
SOLVERS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1053
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
AEROTHERMAL MANAGEMENT OF VEHICLE HEAT EXCHANGERS - PARAMETRIC ANALYSIS
Khaled, Mahmoud
El Hage, Hicham
El Marakbi, Ahmed
Harambat, Fabien
Peerhossaini, Hassan
This paper presents a numerical analysis focused on the relation between non-uniformities in flow velocity and temperature distributions upstream of heat exchangers and their thermal performance. For this purpose, a two-dimensional computation code is developed to compute thermal performance, knowing the air flow velocity distribution upstream of an air-liquid heat exchanger, the heat exchanger liquid flow rate and the air and liquid inlet temperatures. A parametric analysis is then presented of the relation between the thermal performance of the heat exchanger and the different parameters above. It is found that non-uniformities in air velocity and water flow distributions can decrease the thermal performance of a heat exchanger from 33 to 42%. However, non-uniformity in the air temperature distribution can increase thermal performance by up to 5%.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/51
info:doi/10.1115/FEDSM2013-16148
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION FLOW
THERMAL PERFORMANCE
OPTIMIZATION
DESIGN
ALGORITHMS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1055
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
EXPERIMENTAL AND NUMERICAL STUDY OF THE COOLANTS DISTRIBUTOR FOR MACHINING PROCESS
Moussa, Tala
Dellavalle, Dominique
Garnier, Bertrand
Peerhossaini, Hassan
Grinding is a machining process which may encounter excessive heat generated by the friction between the wheel and the material, and therefore degrade the tool as well as the material. The heat has hence, to be removed as efficiently as possible, most often by external cooling. The fluid is projected on the hot interface between the tool and the material through a curved duct coolant distributor. The performance of such a system is strongly dependent on the fluid flow in the curved duct and on the impinging jet flow properties. To optimize cooling setup, CFD simulations and in-situ experiments using particle image velocimetry (Ply) have been made, as well as global flow rate and pressure measurements in the curved duct. A three-dimensional model of a curved duct with 25 outlet nozzles has been studied for duct Reynolds number up to 100,000. Different geometrical configurations for various nozzle diameters have been studied. Due to the complexity of the distributor geometry, it is shown that the global hydraulic balance is not appropriate for sizing the industrial process. On the contrary, satisfactory trend matching in fluid flow streamline behavior is between numerical and experimental results, and an accurate prediction of the pressure drop both show that the numerical simulation is reliable to capture the flow pattern within the curved channel distributor.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/53
info:doi/10.1115/FEDSM2013-16354
Civil and Environmental Engineering Publications
Scholarship@Western
CRITICAL HEAT-FLUX
GORTLER INSTABILITY
U-BEND
TRANSFER ENHANCEMENT
JET IMPINGEMENT
TURBULENT-FLOW
AIR-JET
MODES
PLATE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1056
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
A semi-analytical approach for temperature distribution in Dean flow
Habchi, Charbel
Khaled, Mahmoud
Lemenand, Thierry
Della Valle, Dominique
Elmarakbi, Ahmed
Peerhossaini, Hassan
Numerical simulations of the flow field and heat transfer require the conjugate solution of the Navier-Stokes and energy equations, a highly compute-intensive process. Here a semi-analytical approach is proposed to solve the energy equation in curved pipes. It requires the flow velocity field, the wall temperature, and the temperature at only one point of the flow cross-section to provide the entire temperature field.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/54
info:doi/10.1007/s00231-013-1222-z
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION FLOW
HEAT-TRANSFER
CURVED PIPE
FLUID
TUBES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1057
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
LOW FREQUENCY ACOUSTIC STREAMING IN A HELE-SHAW CELL
Costalonga, Maxime
Peerhossaini, Hassan
Brunet, Philippe
When an acoustic wave propagates in a fluid, it can generate a second order flow which characteristic time is much longer than the period of the wave. Within a range of frequency between 1 and several hundred Hz, a relatively simple and versatile way to generate streaming flow is to put a vibrating object in the fluid. The flow develops vortices in the viscous boundary layer located in the vicinity of the source of vibrations, which in turns leads to an outer irrotational streaming denoted as Rayleigh streaming. Due to that the flow originates from non-linear time-irreversible terms of the Navier-Stokes equation, this phenomenon can be used to move fluids and even to generate efficient mixing at low Reynolds number, for instances in confined geometries. Here we report an experimental study of such streaming flow in a Hele-Shaw cell of 2 millimeters span using long exposure flow visualization and PIV measurements. Our study is especially focused on the effects of acoustic frequency and amplitude on flow dynamics. It is shown that some features of this flow can be predicted by simple scaling arguments, invoking a balance between viscous dissipation in the boundary layer and inertia term, and that acoustic streaming facilitates the generation of vortices.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/55
info:doi/10.1115/FEDSM2014-21384
Civil and Environmental Engineering Publications
Scholarship@Western
CYLINDER
WAVES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1046
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mixing assessment by chemical probe
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Khaled, Mahmoud
Elmarakbi, Ahmed
Peerhossaini, Hassan
Quantification of micro-mixing is a fundamental issue in industrial chemical processes. Local mixing that is not "fast enough" compared with the reaction kinetics reduces the selectivity of the reaction. Micro-mixing can be characterized by chemical probe methods based on observation of a local chemical reaction that results from the competition between turbulent mixing at micro-scales and the reaction kinetics. However, real-world experimental conditions rarely comply with the grounding assumptions of this method. Starting from physical considerations, the present study aims to establish some guidelines for obtaining quantitative information from the chemical probe and for improving the accuracy of the method by an adaptive protocol. For the first aspect, an analytical approach is proposed to define the validity domain based on analysis of the turbulent time scales. For the second purpose, a novel experimental procedure is suggested that entails targeting the concentrations of the chemical species that can provide the optimal conditions for a relevant use of the chemical probe. (C) 2013 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/44
info:doi/10.1016/j.jiec.2013.07.026
Civil and Environmental Engineering Publications
Scholarship@Western
ASSESSING MICROMIXING EFFICIENCY
COMPETING REACTION SYSTEM
IODATE REACTION SYSTEM
GORTLER INSTABILITY
IODIDE
VORTICITY
MODEL
FLOW
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1047
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mass transfer and emulsification by chaotic advection
Lemenand, Thierry
Habchi, Charbel
Della Valle, Dominique
Bellettre, Jerome
Peerhossaini, Hassan
This study characterizes a new mixing process based on chaotic advection for the production of water/oil (w/o) emulsified engine fuel. At low and intermediate Reynolds numbers, in curved pipes, Dean roll-cells induce radial convective mass transfer, a mechanism exploited in the technology of helical static mixers. The succession of bends of alternating curvature planes produces in addition spatially chaotic flow trajectories that enhance the mixing over and above that in the reference helically coiled geometry made of coplanar bends. This feature is assessed in the present work by comparison of the droplet sizes obtained in helical (regular) and alternating (chaotic) static mixers of the same cross section and the same tube length. The coils are assembled from 90 degrees bends, and the chaotic configuration is obtained by turning each bend by +/- 90 degrees with respect to the previous one. To cover a large range of Reynolds numbers [30-350] and capillary numbers [0.1-1], a lipophilic solvent (Butanol) is added to the continuous phase (oil) to decrease the viscosity and a surfactant (Tween 20) is used beyond the critical concentration (covering the whole w/o interface) to decrease the interfacial tension. Drop-size measurements at the exit of the mixer in the chaotic advection configuration show substantial drop-size reduction and tightening in drop-size distribution. Moreover, it is shown that mixing intensification by chaotic advection is almost independent of Reynolds number in the studied range, with a mixing efficiency enhancement around 30%. (C) 2013 Elsevier Ltd. All rights reserved.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/45
info:doi/10.1016/j.ijheatmasstransfer.2013.12.015
Civil and Environmental Engineering Publications
Scholarship@Western
2 IMMISCIBLE FLUIDS
HEAT-TRANSFER
DROPLETS FORMATION
STATIC MIXERS
FLOW
DISPERSION
TUBES
PIPE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1051
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
TRANSPORT PHENOMENA IN PASSIVELY MANIPULATED CHAOTIC FLOWS: SPLIT-AND-RECOMBINE REACTORS
Ghanem, Akram
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Static mixers and multifunctional heat exchangers/reactors are being used increasingly in process industries. In the inertial or turbulent regime, mixers often incorporate inserts or corrugated walls whose primary function is to create embedded flow vorticity. On the other hand, in low-Reynolds-number flows, for viscosity or residence time purposes, it is necessary to provide solutions based on kinematic mixing, i.e. the topology of the primary flow, such as split-and-recombine reactors (SAR). The concept is based on passive liquid stream division, then rotation in bends of opposite chiralities, and finally recombination, achieving stretching/folding following the baker's transform. Mixing is efficiently ensured by diffusion without generating prohibitive pressure drops. In this work, a chemical probe is used to study mixing and mass transfer in two different split-and-recombine square duct geometries, SAR-1 and SAR-2 of 3 mm side. Results show that effective mass transfer and mixing can be achieved with a short reactor length and moderate pressure losses; the SAR-1 geometry being more efficient. The chaotic configurations are a good compromise even for higher Reynolds numbers compared to static mixers operating in the transitional regime: they produce moderate pressure losses while enhancing mass transfer.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/49
info:doi/10.1115/FEDSM2013-16077
Civil and Environmental Engineering Publications
Scholarship@Western
MICROMIXING EFFICIENCY
REACTION SYSTEM
ADVECTION FLOW
MODEL
NUMBER
MIXER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1048
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Sensitivity and applications of a new method for the simultaneous measurement of convective and radiative heat flux in underhood applications-toward multiple versions
Khaled, M.
Al Shaer, A.
Ramadan, M.
Elmarakbi, A.
Harambat, F.
Peerhossaini, H.
Convective and radiative heat fluxes enter simultaneously into most thermal engineering applications, especially in the vehicle underhood. However, separate measurements of these fluxes are needed for understanding and analyzing underhood aerothermal phenomena. In this context, a new experimental technique has been proposed (Khaled et al 2010 Meas. Sci. Technol. 21 025903) that allows the simultaneous measurement of convective and radiative heat fluxes. The technique uses a pair of fluxmeters with different radiative properties: the two fluxmeters measure the same convective flux but different radiative fluxes proportional to the fluxmeters' emissivities. This permits the separate calculation of the convective and radiative fluxes. This paper presents a sensitivity and applicability analysis of the new technique, taking into account the effects of a number of parameters such as emissivities, the precision of emissivity estimation and the difference in convective heat fluxes due to fluxmeter position. Also, new applications of this novel technique are proposed as an alternative when the initial version becomes inaccurate.
2014-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/46
info:doi/10.1088/0957-0233/25/3/035901
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1054
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
AEROTHERMAL ANALYSIS OF VEHICLE THERMAL SOAK: TEMPERATURE AND HEAT-FLUX MEASUREMENTS
Khaled, Mahmoud
Habchi, Charbel
El Hage, Hicham
El Marakbi, Ahmed
Harambat, Fabien
Peerhossaini, Hassan
This paper presents an experimental investigation of the underhood thermal behaviors during vehicle thermal soak (when the vehicle stops after a large thermal load) by temperature measurement and separate measurements of convective and radiative heat fluxes. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France. The underhood is instrumented by almost 120 surface and air thermocouples and 20 fluxmeters. Measurements are performed for three thermal functioning conditions, with the engine in operation and the front wheels positioned on the test facility with power-absorption controlled rollers. It was found that in thermal soak the temperature of certain components can increase by almost 80 degrees C (pre-catalyst screen) and that of air zones by almost 40 degrees C (crawl area).
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/52
info:doi/10.1115/FEDSM2013-16124
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1058
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
MIXING ENHANCEMENT IN A CHAOTIC MICROMIXER USING PULSATING FLOW
Karami, Mohammad
Jarrahi, Mojtaba
Shirani, Ebrahim
Peerhossaini, Hassan
This study determines the simultaneous effects of spatial disturbance and flow pulsation on micromixing by using three different metrics: concentration distribution, Lyapunov exponent and axial vorticity. Numerical simulations are performed for both steady and pulsating flows through a microchannel made up of C-curved repeating units. Moreover, a straight microchannel is analyzed to compare the effects of chaotic advection and molecular diffusion, the main mechanisms of transverse mixing in the chaotic and straight mixer respectively. Simulations are carried out in the steady flow for the Reynolds number range 1 <= Re <= 50 and in the pulsating flow for velocity amplitude ratios 1 <=beta <= 2.5, and the ratio of the peak oscillatory velocity component to the mean flow velocity, Strouhal numbers 0.1 <= St <= 0.5. It was found that chaotic advection improves mixing without significant increase in pressure drop. The analysis of concentration distribution implied that full mixing occurs after Reynolds number 50 in the steady flow. When the flow is pulsatile, small and moderate values of the Strouhal number (0.1 <= St <= 0.3) and high values of velocity amplitude ratio (beta >= 2) are favorable conditions for mixing enhancement. Moreover, mixing has an oscillating trend along the microchannel due to the coexistence of regular and chaotic zones in the fluid. These results correlate closely with those obtained using two other metrics, analysis of the Lyapunov exponent and axial vorticity.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/56
info:doi/10.1115/FEDSM2014-21360
Civil and Environmental Engineering Publications
Scholarship@Western
DESIGN
MIXER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1059
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
CHAOTIC HEAT TRANSFER IN A LAMINAR PULSATING FLOW WITH CONSTANT WALL TEMPERATURE
Karami, Mohammad
Jarrahi, Mojtaba
Habibi, Zahra
Shirani, Ebrahim
Peerhossaini, Hassan
The correlation between heat transfer enhancement and secondary flow structures in laminar flows through a chaotic heat exchanger is discussed. The geometry consists of three bends; the angle between curvature planes of successive bends is 90 degrees. Numerical simulations are performed for both steady and pulsating flows when the walls are subjected to a constant temperature. The temperature profiles and secondary flow patterns at the exit of bends are compared in order to characterize the flow. Simulations are carried out for the Reynolds numbers range 300 <= Re <= 800, velocity amplitude ratios (the ratio of the peak oscillatory velocity component to the mean flow velocity) 1 <=beta <= 2.5, and wall temperatures 310 <= T-w(K) <= 360. The results show that in the steady flow, heat transfer enhancement occurs with increasing Reynolds number and wall temperature. However, heating homogenization becomes almost independent of Reynolds number when homoclinic connections exist in the flow. Moreover, at high values of wall temperature, heat transfer enhancement is greater than mixing improvement due to the presence of homoclinic connections. In the pulsating flow, Nusselt number improves with beta, and beta >= 2 is a sufficient condition for heat transfer enhancement. The formation and development of homoclinic connections are correlated with the heating homogenization.
2014-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/57
info:doi/10.1115/FEDSM2014-21358
Civil and Environmental Engineering Publications
Scholarship@Western
TRANSFER ENHANCEMENT
TURBULENT-FLOW
PIPE
ADVECTION
EXCHANGER
CONVECTION
CHANNEL
TUBE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1061
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mixing enhancement by pulsating chaotic advection
Jarrahi, Mojtaba
Castelain, Cathy
Peerhossaini, Hassan
The purpose of this study is to investigate transverse mixing enhancement by superposition of periodic time dependence, in the form of pulsation, on a twisted pipe flow in which the fluid particles trajectories are spatially chaotic. The pulsation makes the secondary flow structure more complex, resulting in stronger velocity gradients that enhance stretching and folding, the main mechanisms of chaotic mixing. Here, the chaotic configuration is six alternating 90 curved pipes. The imposed pulsating conditions range as follows: steady Reynolds numbers 420 <= Re-st <= 1000, velocity component ratios 1 <= (beta = U-max,U-osc/U-m,U-st) <= 4 and frequency parameters 8.37 < (alpha = ro(w/v)(0.5))< 24.5. The secondary velocity fields are measured by particle image velocimetry. The axial vorticity and transverse strain rate at the outlet of each curved pipe in pulsatile flow are compared with those of the steady flows. Analysis of these criteria for mixing assessment shows that beta >= 2 and alpha <= 15 are favourable pulsating conditions for transverse mixing enhancement. Moreover, in some pulsation conditions, the cell centres visit a zone in the flow cross-section that is much larger than in the steady case, implying that pulsation also contributes to mixing homogenization. (c) 2013 Elsevier B.V. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/59
info:doi/10.1016/j.cep.2013.10.003
Civil and Environmental Engineering Publications
Scholarship@Western
CURVED PIPE
OSCILLATORY FLOW
UNSTEADY FLOWS
SECONDARY FLOW
TWISTED PIPE
STENOSIS
REGIME
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1063
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Thermal analysis of chemical reactions in microchannels using highly sensitive thin-film heat-flux microsensor
Ammar, Houssein
Garnier, Bertrand
el Moctar, Ahmed Ould
Willaime, Herve
Monti, Fabrice
Peerhossaini, Hassan
Heat transfer in microfluidic devices and hence miniaturized thermal sensors has been widely analyzed in the last decade and is of great importance in applications such as micro-heat exchangers and microreactors. Here we report on some improvements in temperature measurement techniques, which can be the source of large errors due to their intrusiveness and the unreliability of conventional miniaturized thermal sensors. Gold thin films were deposited on a borosilicate substrate to create a low-cost, less intrusive 2D heat flux and temperature sensor for heat-transfer measurement along the main flow and within a microchannel. The performance of the new device for the thermal analysis inside a microreactor is illustrated with a neutralization reaction. The global heat flux released by the exothermal reaction is measured as a function of the flow rate and the reaction enthalpy is deduced. For a well studied acid-base reaction, the reaction enthalpy measured using this new heat-flux sensor had only a 5% discrepancy with the standard value, showing the efficiency of the new thin-film device. (c) 2013 Elsevier Ltd. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/61
info:doi/10.1016/j.ces.2013.02.055
Civil and Environmental Engineering Publications
Scholarship@Western
FLOW
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1060
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Comparative efficiency of shear, elongation and turbulent droplet breakup mechanisms: Review and application
Lemenand, T.
Dupont, P.
Della Valle, D.
Peerhossaini, H.
The study of phase dispersion of two immiscible fluids in different flows requires identifying the relevant breakup mechanisms. We propose here a detailed investigation of droplet breakup in a multifunctional exchanger-reactor of the vortex generator type in which transfer intensification is due to longitudinal vortical structures. We compare the efficiency of the mean gradients and turbulent mechanisms in droplet breakup in this industrial reactor. This efficiency is essentially characterized by the resulting distribution of droplet diameters. Then, the roles of the mean flow and the turbulent field, intensity, energy spectrum, and turbulence scales are examined in relation to the liquid/liquid dispersion in order to explore the governing mechanisms of drop breakup. In the complex flow considered here - nonhomogeneous and anisotropic turbulence at moderate Reynolds numbers (<15,000) - with weak turbulence intensity (about 10%), it can be demonstrated that turbulent breakup mechanisms largely dominate mean flow effects; elongation and shear effects are shown to have minor effects on the breakup mechanisms. Moreover, the global characteristic scales of the flow are not the relevant parameters in predicting the final size of the emulsion, but instead the Kolmogorov microscale, implying that the residence time in the reactor is not a limiting factor. Hence, the local dissipation rate governs the performance of the actual multifunctional reactor. This study provides some insight in the design and scaling-up of multiphase reactors. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/58
info:doi/10.1016/j.cherd.2013.03.017
Civil and Environmental Engineering Publications
Scholarship@Western
DISPERSED-PHASE VISCOSITY
2 IMMISCIBLE FLUIDS
STATIC MIXER
BUBBLE BREAKUP
FLOW
SIZE
COALESCENCE
DEFORMATION
VORTICITY
INERTIA
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1065
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Partitioned solver for strongly coupled fluid-structure interaction
Habchi, Charbel
Russeil, Serge
Bougeard, Daniel
Harion, Jean-Luc
Lemenand, Thierry
Ghanem, Akram
Della Valle, Dominique
Peerhossaini, Hassan
In this work a fluid-structure interaction solver is developed in a partitioned approach using block Gauss-Seidel implicit scheme. Finite volume method is used to discretize the fluid flow problem on a moving mesh in an arbitrary Lagrangian-Eulerian formulation and by using an adaptive time step. The pressure-velocity coupling is performed by using the PIMPLE algorithm, a combination of both SIMPLE and PISO algorithms, which permits the use of larger time steps in a moving mesh. The structural elastic deformation is analyzed in a Lagrangian formulation using the St. Venant-Kirchhoff constitutive law, for non-linear large deformations. The solid structure is discretized by the finite volume method in an iterative segregated approach. The automatic mesh motion solver is based on Laplace smoothing equation with variable mesh diffusion. The strong coupling between the different solvers and the equilibrium on the fluid-structure interface are achieved by using an iterative implicit fixed-point algorithm with dynamic Aitken's relaxation method. The solver, which is called vorflexFoam, is developed using the open source C++ library OpenFOAM. The solver is validated on two different benchmarks largely used in the open literature. In the first one the structural deformation is induced by incompressibility. The second benchmark consists on a vortex excited elastic flap in a Von Karman vortex street. Finally, a more complex case is studied including two elastic flaps immersed in a pulsatile flow. The present solver detects accurately the interaction between the complex flow structures generated by the flaps and the effect of the flaps oscillations between each other. (c) 2012 Elsevier Ltd. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/63
info:doi/10.1016/j.compfluid.2012.11.004
Civil and Environmental Engineering Publications
Scholarship@Western
STRUCTURE SYSTEMS
FORMULATION
ALGORITHMS
SIMULATION
FLOWS
MASS
FACTORIZATION
EQUATIONS
DYNAMICS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1066
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
EFFECTS OF GROUND VEHICLE INCLINATION ON UNDERHOOD COMPARTMENT COOLING
Khaled, M.
Alshaer, A.
Hachem, F.
Harambat, F.
Peerhossaini, H.
This work reports on experiments carried out on a real passenger vehicle in a large wind tunnel to investigate the effects of car inclination on underhood cooling. The vehicle's underhood is instrumented by thermocouples that measure the temperatures of many underhood components during different car functioning modes. Measurements are carried out for three thermal functioning points at car speeds 90,110 and 130 km/h. In these experiments the engine was in operation and the front wheels positioned on the test facility with power-absorption-controlled rollers. Three car inclinations are investigated: flat, uphill and downhill. The results show that car inclination, even if very small, can have significant effects on underhood cooling and must be taken into consideration in numerical simulations and controlled in experimental tests. It was shown that down-hill and up-hill inclinations increase temperatures of components, air zones and engine parameters in the underhood, with higher effect for the down-hill inclination. Temperature increases in constant-speed driving phase are higher than in thermal soak phase.
2012-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/64
info:doi/10.1007/s12239-012-0090-8
Civil and Environmental Engineering Publications
Scholarship@Western
SYSTEM
TEMPERATURE
DIESEL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1068
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Enhancing heat transfer in vortex generator-type multifunctional heat exchangers
Habchi, Charbel
Russeil, Serge
Bougeard, Daniel
Harion, Jean-Luc
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Global and local analysis of the heat transfer in turbulent vortical flows is studied using three-dimensional numerical simulations. Vorticity is generated by inclined vortex generators in a turbulent circular pipe flow with twelve different configurations that fall into three categories. In the first category are rows of trapezoidal vortex generators in different arrangements; in the second category the vortex generators are fixed at certain distance from the tube wall, and the third category has vortex generator rows between which a row of small protrusions are inserted on the tube wall. First, a global analysis of the thermal performance is performed for all these configurations, which are also compared with other heat exchangers from the literature. New correlations for the friction factor and Nusselt number are then obtained. Local analysis of the effect of the flow structure on the temperature distribution is carried out for the four configurations showing the best performances. The local analysis involves studying the streamwise vorticity flux to characterize the convective transport process, the turbulent kinetic energy characterizing the turbulent mixing, and finally the local Nusselt number. (C) 2012 Elsevier Ltd. All rights reserved.
2012-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/66
info:doi/10.1016/j.applthermaleng.2012.01.020
Civil and Environmental Engineering Publications
Scholarship@Western
CIRCULAR TUBE
STATIC MIXER
FLOW
ENHANCEMENT
VORTICITY
INSERTS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1069
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Fan air flow analysis and heat transfer enhancement of vehicle underhood cooling system - Towards a new control approach for fuel consumption reduction
Khaled, Mahmoud
Mangi, Fareed
El Hage, Hisham
Harambat, Fabien
Peerhossaini, Hassan
We report here experimental results focused on the optimization of vehicle underhood cooling module. These results constitute the basis for a new approach of controlling the cooling module positioning according to the engine energy requirements. Measurements are carried out on a simplified vehicle body designed based on the real vehicle front block. We report here velocity and temperature measurements by Particle Image Velocimetry (Ply), by Laser Doppler Velocimetry (LDV) and by thermocouples. The underhood of the simplified body is instrumented by 59 surface and fluid thermocouples. Measurements are carried out for conditions simulating both the slowdown and the thermal soak phases with the fan in operation. Different fan rotational speeds, radiator water flow and underhood geometries have been experimented. The ultimate aim is to apply the new control approach to a real vehicle so as to reduce the energy delivered to the pump and compressor and therefore to reduce the vehicle fuel consumption. (C) 2011 Elsevier Ltd. All rights reserved.
2012-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/67
info:doi/10.1016/j.apenergy.2011.10.017
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION FLOW
THERMAL PERFORMANCE
EXCHANGER
OPTIMIZATION
DESIGN
ALGORITHMS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1077
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Entropy production and field synergy principle in turbulent vortical flows
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Pacheco, Leonardo
Le Corre, Olivier
Peerhossaini, Hassan
The heat transfer in turbulent vortical flows is investigated by three different physical approaches. Vortical structures are generated by inclined baffles in a turbulent pipe flow, of three different configurations. In the first, the vortex generators are aligned and inclined in the flow direction (called the reference geometry); in the second, a periodic 45 degrees rotation is applied to the tab arrays (alternating geometry); the third is the reference geometry used in the direction opposite to the flow (reversed geometry). The effect of the flow structure on the temperature distribution in these different configurations is analyzed. The conventional approach based on heat-transfer analysis using the Nusselt number and the enhancement factor is used to determine the efficiency of these geometries relative to other heat exchangers in the literature. The effect of vorticity on the Nusselt number is clearly demonstrated, and so as to highlight the respective roles of the coherent structures and the turbulence, a new parameter is defined as the ratio of the vortex circulation to the turbulent viscosity. The relative contribution of the radial convection to heat transfer appears to increase with Reynolds number. The effect of mixing performance on the temperature distribution is investigated by the field synergy method. A global parameter, namely the intersection angle between the velocity and temperature gradient, is defined in order to compare performances. Finally, an analysis of energetic efficiency by entropy production, involving both heat transfer and pressure losses, is carried out to determine the overall performance of the heat exchangers. All these approaches lead to the same conclusion: that the reversed geometry presents the best heat transfer coefficient and the best energetic efficiency. The reference geometry shows the worst performance, and the alternating array has intermediate performance. (C) 2011 Elsevier Masson SAS. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/75
info:doi/10.1016/j.ijthermalsci.2011.07.012
Civil and Environmental Engineering Publications
Scholarship@Western
CONVECTIVE HEAT-TRANSFER
LONGITUDINAL VORTEX GENERATOR
2 IMMISCIBLE FLUIDS
TRANSFER ENHANCEMENT
GORTLER INSTABILITY
STATIC MIXER
TRANSFER AUGMENTATION
RECTANGULAR CHANNEL
CIRCULAR TUBE
SHEAR FLOWS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1078
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Spatial optimization of an underhood cooling module - Towards an innovative control approach
Khaled, Mahmoud
Harambat, Fabien
El Hage, Hicham
Peerhossaini, Hassan
The present paper reports a numerical investigation of spatial optimization of heat-exchanger by acting on its positioning in the vehicle's cooling module. This analysis also elucidates how to act on the different parameters influencing heat-exchanger performance in order to optimize their functioning. A two-dimensional computation code permits optimizing the performance of the cooling module by positioning different heat exchangers, in both the driving and stop phases of the vehicle. The ultimate aim is to apply new control approaches to real vehicles so as to reduce pump and compressor energy consumption and thus fuel consumption. Compared to a reference "in-series" configuration of the cooling module HXs (in which the different HXs are superposed in the airflow direction), an "in-parallel" configuration (in which the different HX surfaces are in a row with respect to the air flow direction) increases the thermal power of the HXs by 4.4% and decreases the pressure losses by 0.9%. (C) 2011 Elsevier Ltd. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/76
info:doi/10.1016/j.apenergy.2011.04.025
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION FLOW
HEAT-EXCHANGER
THERMAL PERFORMANCE
DESIGN
ALGORITHMS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1080
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
A new adaptive procedure for using chemical probes to characterize mixing
Habchi, Charbel
Della Valle, Dominique
Lemenand, Thierry
Anxionnaz, Zoe
Tochon, Patrice
Cabassud, Michel
Gourdon, Christophe
Peerhossaini, Hassan
The iodide-iodate chemical probe method is modified by a novel adaptive procedure to investigate the mixing abilities of two compact curved-duct reactors. Both reactors have a rectangular cross section; the first has smooth curvature (called the wavy duct) and the second has sharper bends (zigzag duct). In the conventional procedure, this method is used to characterize local micro-mixing, and for all experiments (for different Reynolds numbers and injection points) the reagent initial concentrations are kept at the same values. Even with wall injection, the selectivity of the chemical system is generally improved by increasing the flow Reynolds number. Nevertheless, two limitation sencountered in using chemical probes (with the conventional protocol) tocharacterize the mixing abilities of the present reactors that prevent the conventional protocol of the chemical probe from discriminating between the mixing abilities of the two mockups. First, the duct walls are corrugated, so that the wall injection used to measure local micro-mixing is affected by the wall roughness, independently of the Reynolds number. Second, the flow Reynolds numbers are relatively low due to the small size of the duct sides, so that the measurements are inevitably hindered by meso-mixing effects. The challenge is thus to adapt the chemical method for characterizing the global mixing, by enlarging the measurement volumes o as to capture and take into account all mixing scales. In the new adaptive procedure, the kinetics of the second reaction are adjusted in such away as to impose the same reactive volume for different Reynolds numbers, leading to more relevant results for the segregation index XS. Experimental results reveal that the mixing performance of the zigzag channel as assessed by this method is slightly above that of the wavy one. Finally, these gregation indexin both reactor sisrelated to the mixing time tm by using a physical model in the literature. (C) 2011 ElsevierLtd. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/78
info:doi/10.1016/j.ces.2011.04.019
Civil and Environmental Engineering Publications
Scholarship@Western
ASSESSING MICROMIXING EFFICIENCY
MULTIFUNCTIONAL HEAT-EXCHANGERS
COMPETING REACTION SYSTEM
CHAOTIC ADVECTION FLOW
IODATE REACTION SYSTEM
2 IMMISCIBLE FLUIDS
STREAMWISE VORTICITY
GORTLER INSTABILITY
DROPLETS FORMATION
TWISTED PIPE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1082
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Secondary flow patterns and mixing in laminar pulsating flow through a curved pipe
Jarrahi, Mojtaba
Castelain, Cathy
Peerhossaini, Hassan
Mixing by secondary flow is studied by particle image velocimetry (PIV) in a developing laminar pulsating flow through a circular curved pipe. The pipe curvature ratio is eta = r (0)/r (c) = 0.09, and the curvature angle is 90A degrees. Different secondary flow patterns are formed during an oscillation period due to competition among the centrifugal, inertial, and viscous forces. These different secondary-flow structures lead to different transverse-mixing schemes in the flow. Here, transverse mixing enhancement is investigated by imposing different pulsating conditions (Dean number, velocity ratio, and frequency parameter); favorable pulsating conditions for mixing are introduced. To obviate light-refraction effects during PIV measurements, a T-shaped structure is installed downstream of the curved pipe. Experiments are carried out for the Reynolds numbers range 420 a parts per thousand currency sign Re-st a parts per thousand currency sign 1,000 (Dean numbers 126.6 a parts per thousand currency sign Dn a parts per thousand currency sign 301.5) corresponding to non-oscillating flow, velocity component ratios 1 a parts per thousand currency sign (beta = U (max,osc)/U (m,st)) a parts per thousand currency sign 4 (the ratio of velocity amplitude of oscillations to the mean velocity without oscillations), and frequency parameters 8.37 < (alpha = r (0)(omega/nu)(0.5)) < 24.5, where alpha(2) is the ratio of viscous diffusion time over the pipe radius to the characteristic oscillation time. The variations in cross-sectional average values of absolute axial vorticity (|zeta|) and transverse strain rate (|epsilon|) are analyzed in order to quantify mixing. The effects of each parameter (Re-st, beta, and alpha) on transverse mixing are discussed by comparing the dimensionless vorticities (|zeta (P) |/|zeta (S) |) and dimensionless transverse strain rates (|epsilon (P) |/|epsilon (S) |) during a complete oscillation period.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/80
info:doi/10.1007/s00348-010-1012-z
Civil and Environmental Engineering Publications
Scholarship@Western
OSCILLATORY FLOW
UNSTEADY FLOWS
ENTRANCE FLOW
PERIODIC-FLOW
VISCOUS-FLOW
TUBES
DISPERSION
FLUID
CURVATURE
STENOSIS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1067
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Some innovative concepts for car drag reduction: A parametric analysis of aerodynamic forces on a simplified body
Khaled, Mahmoud
El Hage, Hicham
Harambat, Fabien
Peerhossaini, Hassan
The aerodynamic torsor of a vehicle is among the most crucial parameters in new car development. This torsor has been decreased over the years by more than 33%, but beyond that further improvement has become difficult and challenging for car manufacturers. In this context, the present paper focuses on a parametric analysis of the trends in the aerodynamic forces. We report here aerodynamic force measurements carried out on a simplified vehicle model. Tests were performed in wind tunnel S4 of Saint-Cyr l'Ecole for different airflow configurations in order to isolate the parameters that affect the aerodynamic torsor and to confirm others previously suspected. The simplified model has flat and flexible air inlets and several types of air outlet, and includes in its body a real cooling system and a simplified engine block that can move in the longitudinal and lateral directions. The results of this research, which can be applied to any new car design, show configurations in which the overall drag coefficient can be decreased by 2%, the aerodynamic cooling drag coefficient by more than 50% and the lift coefficient by 5%. Finally, new designs for aerodynamic drag reduction, based on the combined effects of the different parameters investigated, are proposed. (C) 2012 Elsevier Ltd. All rights reserved.
2012-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/65
info:doi/10.1016/j.jweia.2012.03.019
Civil and Environmental Engineering Publications
Scholarship@Western
SHAPE OPTIMIZATION
ROAD VEHICLES
WIND-TUNNEL
FLOW
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1064
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Measurement and model on thermal properties of sintered diamond composites
Moussa, Tala
Garnier, Bertrand
Peerhossaini, Hassan
A prelude to the thermal management of grinding processes is measurement of the thermal properties of working materials. Indeed, tool materials must be chosen not only for their mechanical properties (abrasion performance, lifetime...) but also for thermal concerns (thermal conductivity) for efficient cooling that avoids excessive temperatures in the tool and workpiece. Sintered diamond is currently used for grinding tools since it yields higher performances and longer lifetimes than conventional materials (mineral or silicon carbide abrasives), but its thermal properties are not yet well known. Here the thermal conductivity, heat capacity and density of sintered diamond are measured as functions of the diamond content in composites and for two types of metallic binders: hard tungsten-based and soft cobalt-based binders. The measurement technique for thermal conductivity is derived from the flash method. After pulse heating, the temperature of the rear of the sample is measured with a noncontact method (infrared camera). A parameter estimation method associated with a three-layer nonstationary thermal model is used to obtain sample thermal conductivity, heat transfer coefficient and absorbed energy. With the hard metallic binder, the thermal conductivity of sintered diamond increased by up to 64% for a diamond content increasing from 0 to 25%. The increase is much less for the soft binder: 35% for diamond volumes up to 25%. In addition, experimental data were found that were far below the value predicted by conventional analytical models for effective thermal conductivity. A possible explanation is poor heat transfer at the diamond-binder interface. Indeed, better agreement between measurements and model was found by taking into account a thermal contact resistance between matrix and diamond particles equal to 0.75 and 1.25 x 10 (6) m(2) KW (1) for respectively the cobalt- and tungsten-based composites. (C) 2012 Elsevier B.V. All rights reserved.
2013-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/62
info:doi/10.1016/j.jallcom.2012.11.025
Civil and Environmental Engineering Publications
Scholarship@Western
CU/DIAMOND COMPOSITES
CONTACT RESISTANCE
POWDER-METALLURGY
CONDUCTIVITY
PARTICLES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1073
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Heat-Transfer Enhancement by Artificially Generated Streamwise Vorticity
Ghanem, Akram
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Vortex-induced heat transfer enhancement exploits longitudinal and transverse pressure-driven vortices through the deliberate artificial generation of large-scale vortical flow structures. Thermal-hydraulic performance, Nusselt number and friction factor are experimentally investigated in a HEV (high-efficiency vortex) mixer, which is a tubular heat exchanger and static mixer equipped with trapezoidal vortex generators. Pressure gradients are generated on the trapezoidal tab initiating a streamwise swirling motion in the form of two longitudinal counter-rotating vortex pairs (CVP). Due to the Kelvin Helmholtz instability, the shear layer generated at the tab edges, which is a production site of turbulence kinetic energy (TKE), becomes unstable further downstream from the tabs and gives rise to periodic hairpin vortices. The aim of the study is to quantify the effects of hydrodynamics on the heat-and mass-transfer phenomena accompanying such flows for comparison with the results of numerical studies and validate the high efficiency of the intensification process implementing such vortex generators. The experimental results reflect the enhancement expected from the numerical studies and confirm the high status of the HEV heat exchanger and static mixer.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/71
info:doi/10.1088/1742-6596/395/1/012051
Civil and Environmental Engineering Publications
Scholarship@Western
FLOW
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1074
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
A novel thin-film temperature and heat-flux microsensor for heat transfer measurements in microchannels
Hamadi, David
Garnier, Bertrand
Willaime, Herve
Monti, Fabrice
Peerhossaini, Hassan
Temperature and heat-flux measurement at the microscale for convective heat-transfer studies requires highly precise, minimally intrusive sensors. For this purpose, a new generic temperature and heat-flux sensor was designed, calibrated and tested. The sensor allows measurement of temperature and heat flux distributions along the direction of flow. It is composed of forty gold thermoresistances, 85 nm thick, deposited on both sides of a borosilicate substrate. Their sensitivities are about 37.8 mu VK-1, close to those of a K-type wire thermocouple. Using a thermoelectrical model, temperature biases due to the Joule effect were calculated using the current crossing each thermoresistance and the heat-transfer coefficient. Finally, heat-transfer measurements were performed with deionized water flowing in a straight PDMS microchannel for various Reynolds numbers. The Nusselt number was obtained for microchannels of 50 to 10 mu m span. The results were found to be in good agreement with classical Nu-Re macroscopic correlations.
2012-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/72
info:doi/10.1039/c2lc20919e
Civil and Environmental Engineering Publications
Scholarship@Western
FORCED-CONVECTION
FLOW
WATER
MICROTUBES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1071
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
VORTICALLY ENHANCED HEAT TRANSFER AND MIXING: STATE OF THE ART AND RECENT RESULTS
Ghanem, Akram
Lemenand, Thierry
Della Valle, Dominique
Habchi, Charbel
Peerhossaini, Hassan
Longitudinal and transverse pressure-driven vortices induced by shear instabilities behind vortex generators play a crucial role in convective transport phenomena. The proven influence of these turbulence promoters on heat and mass transfer enhancement has led to their incorporation in modem multifunctional heat exchangers/reactors. The purpose of this work is to demonstrate experimentally the effects of hydrodynamics on the transfer processes accompanying such flows. The high-efficiency vortex (HEV) is an innovative static mixer and a low-energy-consumption heat exchanger designed to exploit these types of vortices. Results obtained in turbulent flow with embedded vorticity in an REV static mixer are compared with numerical results in the literature. Both numerical and experimental results confirm the high energy efficiency of the REV static mixer flow.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/69
Civil and Environmental Engineering Publications
Scholarship@Western
FLOW STRUCTURE
TAB
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1079
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Mass transfer and mixing by pulsatile three-dimensional chaotic flow in alternating curved pipes
Timite, Brahim
Castelain, Cathy
Peerhossaini, Hassan
We present an experimental and numerical study of three-dimensional pulsatile flow in a twisted pipe in order to show the effects of chaotic advection on mixing in this flow configuration. The numerical study is done by CFD code with a pulsatile velocity field imposed as an inlet condition. The experimental setup is composed principally of a "Scotch-yoke" pulsatile flow generator and a twisted duct. The twisted duct consists of six 90 degrees bends of circular cross-section; the plane of curvature of each bend is at 90 degrees to that of its neighbors. The secondary flow, generated by centrifugal force, the pulsating velocity field and also due to the change in curvature plane, leads to irregular fluid particle trajectories. Velocity measurements were made for a range of stationary Reynolds numbers (300 <= Re-st <= 1200) and frequency parameters (1 <= alpha < 20) and for two velocity-amplitude ratios (beta); agreement between the numerical and experimental results is satisfactory. In the first bend, for certain control parameter values, the secondary flow becomes more complex due to the pulsation, and in some cases Lyne instability and a siphon phenomenon appear. However, in the other bends, one passes from four cells (Lyne instability) in the first bend with two cells in the other bends. The numerical and experimental study revealed modifications in the trajectories' evolution due to pulsation. The superposition of an oscillating flow on a stationary curved-pipe flow, in some cases, causes the destruction of the trapping zones (KAM structures). The number of regular zones that disappear with an increase in the number of bends decrease with pulsation frequency and velocity-amplitude ratio. Both these phenomena contribute to the mixing and mass transfer enhancement in the flow. (C) 2011 Elsevier Ltd. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/77
info:doi/10.1016/j.ijheatmasstransfer.2011.04.031
Civil and Environmental Engineering Publications
Scholarship@Western
RESIDENCE TIME DISTRIBUTION
ENTRANCE FLOW
HEAT-TRANSFER
LAMINAR-FLOW
VISCOUS-FLOW
TWISTED PIPE
ADVECTION
TUBES
INSTABILITY
TRANSPORT
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1081
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Laminar Sinusoidal and Pulsatile Flows in a Curved Pipe
Jarrahi, M.
Castelain, C.
Peerhossaini, H.
Two components of pulsatile flow (i.e. steady flow and sinusoidal flow) are studied separately by particle image velocimetry (PIV).The topology of the secondary flow structures, axial vorticities and transverse strain rates in a pure sinusoidal flow and also in a steady flow are compared to those in a pulsatile flow through a curved pipe. The experimental setup provides different conditions for the flow entering a 90 degrees circular curved pipe of diameter 0.04 m and curvature radius 0.22m. Pulsatile flows were studied for two stationary Reynolds numbers, Re-st=420 and Re-st=600. The frequency parameters alpha=10.26 and alpha=14.51 were chosen to study pure sinusoidal flow (alpha=r(0)(omega/v)(0.5)). Pulsating conditions were obtained by combining steady and sinusoidal flow for (Re-st=600, alpha=10.26), (Re-st=600, alpha=14.51) and (Re-st=420, alpha=14.51). The results of this study contribute to a better understanding of mixing in a developing laminar flow through curved pipes (helical and twisted/chaotic mixers) in steady state flow, pure sinusoidal flow and pulsatile flow.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/79
Civil and Environmental Engineering Publications
Scholarship@Western
VISCOUS-FLOW
TUBES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1076
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
THIN-FILM HEAT-FLUX MICROSENSOR FOR HEAT-TRANSFER MEASUREMENT IN MICRO-HEAT EXCHANGERS/MICROREACTORS
Ammar, Houssein
Hamadi, David
Garnier, Bertrand
Ould El Moctar, Ahmed
Peerhossaini, Hassan
Monti, Fabrice
Willaime, Herve
Heat-transfer analysis in microfluidic devices is of great importance in applications such as micro-heat exchangers and microreactors. This work reports on improvements in temperature measurement techniques, which can be the source of large errors due to their intrusiveness and the unreliability of conventional thermal sensors. Gold thin films were deposited on a borosilicate substrate to realize a 2D heat flux sensor for heat-transfer measurement along the main flow within microchannels. Two applications are shown, one related to micro-heat exchangers and the other to microreactors. For the micro-heat exchanger, the effect of length scale on heat transfer in a straight microchannel was investigated and the validity of macroscale correlations for convective heat transfer was checked for deionized water flowing in microchannels of heights 12 to 52 mu m. For the microreactor, the reaction enthalpy of an acid base reaction measured using the new heat-flux sensor had only a 5% discrepancy from the standard value, showing the efficiency of the new thin-film device.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/74
Civil and Environmental Engineering Publications
Scholarship@Western
LAMINAR-FLOW
MICROCHANNELS
TEMPERATURE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1075
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
MIXING, REACTION AND HEAT TRANSFER IN A PULSATILE FLOW MICROREACTOR: INFRARED MEASUREMENTS
Ammar, Houssein
Garnier, Bertrand
Ould El Moctar, Ahmed
Peerhossaini, Hassan
Single-phase microreactors and micro-heat-exchangers have been widely studied over the last decade. Greater safety, better temperature control and hence better reaction products are provided by the high surface-to-volume ratios and compactness of microscale devices, making them more attractive than conventional systems for future industrial applications. Since the flow in microfluidic devices is predominantly laminar long mixing channels or complex geometries are needed for molecular diffusion and completion of the reaction. Hoping to remove this drawback, we demonstrate experimentally the merits of flow pulsation in enhancing mixing efficiency in a simple T channel (50 gm high, 500 gm wide and 40 mm long). For this purpose, a U-shaped PDMS microchannel is enclosed by a 0.1 mm glass plate coated with an opaque layer that constitutes the fourth wall of the microchannel. We investigate experimentally the effect of flow pulsation on mixing of an acid-base neutralization reaction. The mixing of HCl and NaOH reactants, both of 0.8 mol/L concentration, in a T-shaped microchannel is assured by time-pulsed flows at small Reynolds numbers. The effect of mixing is observed at the location along the microchannel at which the temperature reaches its maximum value. For this purpose, infrared thermography, a non-intrusive temperature measurement technique with spatial resolution of a few tens of microns, is used. The mixing efficiency is shown to depend strongly on the ratio between the peak amplitude and the mean flow rate (between 0.4 and 1 mL/h). Saturation is observed for values of this ratio greater than 2.5. Mixing also appears to be enhanced for frequencies of the periodic inlet flows increasing from 1.25 Hz to 5 Hz, i.e. for increasing Strouhal number.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/73
Civil and Environmental Engineering Publications
Scholarship@Western
PHASE FLUID-FLOW
MICROCHANNEL
ENHANCEMENT
MICROMIXERS
PERFORMANCE
REACTORS
CHANNEL
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1083
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Towards the control of car underhood thermal conditions
Khaled, Mahmoud
Harambat, Fabien
Peerhossaini, Hassan
The present paper reports an experimental study of the aerothermal phenomena in the vehicle underhood compartment as investigated by measuring temperature, convective heat flux, and radiative heat flux. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France. The underhood space is instrumented by 120 surface and air thermocouples and 20 fluxmeters. Measurements are performed for three thermal functioning conditions while the engine is in operation and the front wheels are positioned on the test facility with power-absorption-controlled rollers. In the thermal analysis, particular attention is given to measuring absorbed convective heat fluxes at component surfaces. It is shown that, in some components, the outside air entering the engine compartment (for cooling certain components) can in fact heat other components. This problem arises from the underhood architecture, specifically the positioning of some components downstream of warmer components in the same airflow. Optimized thermal management suggests placing these components further upstream or isolating them from the hot stream by deflectors. Given style constraints, however, the use of air deflectors is more suitable than underhood architectural changes. Much of the present paper is devoted to heat flux analysis of the specific thermal behaviours in the underhood compartment (especially the absorption of convective heat fluxes) and to a description of a new control approach exploiting air deflectors to optimize underhood aerothermal management. (C) 2010 Elsevier Ltd. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/81
info:doi/10.1016/j.applthermaleng.2010.11.013
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1084
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Analytical and empirical determination of thermal performance of louvered heat exchanger - Effects of air flow statistics
Khaled, Mahmoud
Harambat, Fabien
Peerhossaini, Hassan
Using the basic equations for modeling heat transfer through heat exchangers, an analytical approach is developed to determining the thermal performance of cross-flow air-cooled heat exchangers as a function of the flow statistics of the upstream cooling air. A two-dimensional computational code is also developed to calculate heat-exchanger performance in relation to the airflow topology upstream of the heat exchanger induced by its integration in complex environments such as the car underhood compartment. The analytical and numerical results show satisfactory agreement: the mean relative error in heat exchanger thermal performance determined by the numerical computation and the analytical approach is about 0.5%. (C) 2010 Elsevier Ltd. All rights reserved.
2011-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/82
info:doi/10.1016/j.ijheatmasstransfer.2010.09.036
Civil and Environmental Engineering Publications
Scholarship@Western
TRANSFER ENHANCEMENT
TRANSFER AUGMENTATION
DESIGN OPTIMIZATION
GENETIC ALGORITHM
TUBE WALL
MALDISTRIBUTION
FINS
EFFICIENCY
WINGLETS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1070
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
ASSESSMENT OF MIXING BY CHEMICAL PROBE IN SWIRL FLOW HEX REACTORS
Ghanem, Akram
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Mixing is a fundamental issue in process engineering and many industrial fields. It is closely related to a large number of different applications, such as chemical reactions, thermal transfer, liquid-liquid extraction, crystallization, and the like. In fact, mixing whether at the reactor scale, sustained by the flow structures, or at molecular scales, influences the selectivity and hence the productivity of reactions. Understanding and quantification of the micromixing mechanism is critical in industrial chemical processes, especially for fast exothermal reactions. Micromixing can be characterized by chemical probe methods based on observation of a local chemical reaction that results from a competition between turbulent mixing at microscales and the reaction kinetics. A system of parallel competing reactions producing iodine was developed by Fournier et al. [1] to study partial segregation in stirred tanks. The coupling of the borate neutralization and the Dushman reaction in this system allows the measurement of micromixing efficiency in reactors by monitoring the amount of iodine produced. Called the iodide-iodate method, this technique has been extensively used in different types of reactors. A novel adaptive procedure recently developed by the authors to improve the reliability of the iodide-iodate method is used here. The heat exchanger-reactor presented here is an innovative geometry based on the addition in parallel of tubes equipped with helical inserts. It is expected to qualify as a low-cost compact heat-exchanger reactor and static mixer of high performance.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/68
Civil and Environmental Engineering Publications
Scholarship@Western
ASSESSING MICROMIXING EFFICIENCY
COMPETING REACTION SYSTEM
IODATE REACTION SYSTEM
PART II
MODEL
TIME
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1072
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
THERMAL PROPERTIES OF SINTERED DIAMOND COMPOSITES USED IN GRINDING
Moussa, Tala
Garnier, Bertrand
Peerhossaini, Hassan
Sintered diamonds are used in grinding because they offer better mechanical properties than conventional materials (mineral or silicon carbide abrasives) and yield high grinding speed and long life. In addition, because of their thermal performance, they contribute to cooling the workpiece, avoiding excessive temperatures. Thus in order to choose the best material for the worktool, one often must know the thermal conductivity of sintered diamond. In this work, the thermal conductivity of sintered diamond is evaluated as a function of the volume fraction of diamond in the composite and for two types of metallic binders: hard and soft. The measurement technique is based on the flash method that associates heating and measurement devices without sample contact and on parameter estimation using a three-layer thermal model. With a hard metallic binder, the thermal conductivity of sintered diamond was found to increase up to 64% for diamond volume fraction increasing from 0 to 25%. The increase is much smaller for the soft binder: 35% for diamond volume reaching 25%. In addition, experimental data were found far below the value predicted by conventional analytical models for effective thermal conductivity. A possible explanation is that the thermal conductivity of such composites is affected by poor heat transfer at the diamond/binder interface, the thermal contact resistance between matrix and diamond particles being estimated at between 0.75 and 1.25 10(-6) m(2)K.W-1.
2012-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/70
Civil and Environmental Engineering Publications
Scholarship@Western
POWDER-METALLURGY
CONDUCTIVITY
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1088
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Turbulent direct-contact heat transfer between two immiscible fluids
Lemenand, Thierry
Durandal, Cedric
Della Valle, Dominique
Peerhossaini, Hassan
Heat transfer between two immiscible liquid phases in turbulent flow is of great interest in improving the residence time, compactness, and energy cost of cooling and heating processes The high-efficiency vortex (HEV) device used here as a direct-contact heat exchanger (DCHE) is a generic multifunctional exchanger/reactor in which wall tabs generate longitudinal vortices responsible for convective radial transfer that enhance macro-mixing, phase dispersion and fast temperature homogenization in the flow. The experiments reported here concern a continuous flow of water in which an immiscible mineral oil is injected. The inlet water temperature ranges from 11 to 13 degrees C, and the inlet oil temperature from 40 to 48 degrees C, the flow Reynolds number varies between 7500 and 15 000 An algebraic one-dimensional thermal model accounting for the axial evolution of the phase temperatures coupled with drop breakup is developed and validated by the experimental thermal results in the DCHE. This model requires knowledge of the turbulent field in single-phase conditions, it can be adapted to other flow geometries and can be used as a sizing tool for engineering design. Despite the phase separation at the outlet, the DCHE is more efficient than a double-jacketed heat exchanger in terms of global Nusselt number. In addition, the HEV heat exchanger is energetically less costly than the other DCHE for the same heat-transfer capacity (C) 2010 Elsevier Masson SAS All rights reserved
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/86
info:doi/10.1016/j.ijthermalsci.2010.05.014
Civil and Environmental Engineering Publications
Scholarship@Western
DISPERSED-PHASE VISCOSITY
CHAOTIC ADVECTION FLOW
DROP-SIZE
GORTLER INSTABILITY
PIPE-FLOW
BREAKUP
LIQUID
EXCHANGERS
INTENSIFICATION
EVAPORATION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1095
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
A new method for simultaneous measurement of convective and radiative heat flux in car underhood applications
Khaled, M.
Garnier, B.
Harambat, F.
Peerhossaini, H.
A new experimental technique is presented that allows simultaneous measurement of convective and radiative heat flux in the underhood. The goal is to devise an easily implemented and accurate experimental method for application in the vehicle underhood compartment. The new method is based on a technique for heat-flux measurement developed by the authors (Heat flow (flux) sensors for measurement of convection, conduction and radiation heat flow 27036-2, (C) Rhopoint Components Ltd, Hurst Green, Oxted, RH8 9AX, UK) that uses several thermocouples in the thickness of a thermal resistive layer (foil heat-flux sensor). The method proposed here uses a pair of these thermocouples with different radiative properties. Measurements validating this novel technique are carried out on a flat plate with a prescribed constant temperature in both natural-and forced-convection flow regimes. The test flat plate is instrumented by this new technique, and also with a different technique that is intrusive but very accurate, used as reference here (Bardon J P and Jarny Y 1994 Procede et dispositif de mesure transitoire de temperature et flux surfacique Brevet n degrees 94.011996, 22 February). Discrepancies between the measurements by the two techniques are less than 10% for both convective and radiative heat flux. Error identification and sensitivity analysis of the new method are also presented.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/93
info:doi/10.1088/0957-0233/21/2/025903
Civil and Environmental Engineering Publications
Scholarship@Western
SENSOR
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1089
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Toward a Competitive Process Intensification: A New Generation of Heat Exchanger-Reactors
Tochon, P.
Couturier, R.
Anxionnaz, Z.
Lomel, S.
Runser, H.
Picard, F.
Colin, A.
Gourdon, C.
Cabassud, M.
Peerhossaini, H.
Della Valle, D.
Lemenand, T.
Toward a Competitive Process Intensification: A New Generation of Heat Exchanger-Reactors - Process Intensification (PI) in chemical production is a major concern of chemical manufacturers. Among the numerous options to intensify a process, the transposition from a batch reactor to a continuous plug flow reactor is a good alternative when the selectivity and the thermal exchange are an issue. In this context, the RAPIC R&D project aims to develop an innovative low-cost component (in the 10 kg/h range). This project deals with the design from the local to the global scale and with testing, from elementary mock-ups to pilot scale. The present paper gives a detailed description of this research project and presents the main results on specification and definition of the reaction channel and the first simple mock-ups.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/87
info:doi/10.2516/ogst/2010020
Civil and Environmental Engineering Publications
Scholarship@Western
STREAMWISE VORTICITY
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1091
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Alternating mixing tabs in multifunctional heat exchanger-reactor
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Streamwise vortices are used in many applications for mixing processes, fast chemical reactions and heat-transfer enhancement. In this work we studied experimentally and numerically the effects of vorticity field redistribution on the turbulence energy dissipation rate in a modified geometry of the high-efficiency vortex (HEV) mixer, in which the mixing tab arrays are periodically rotated by 45 degrees to better distribute the vorticity field. Attention focuses on the evolution and distribution of turbulence energy dissipation, since this describes quantitatively the drop breakup and turbulent micromixing mechanism, which controls fast chemical reactions. It is found that redistribution of the vorticity field locally intensifies turbulent micromixing relative to the classical HEV mixer, producing a local mixing intensification of up to 120%. In addition, the alternating vortex generator arrays improve homogenization of the turbulence field in the mixer. (C) 2009 Elsevier B.V. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/89
info:doi/10.1016/j.cep.2009.07.003
Civil and Environmental Engineering Publications
Scholarship@Western
2 IMMISCIBLE FLUIDS
TRANSFER ENHANCEMENT
GORTLER INSTABILITY
FLOW
TURBULENCE
VORTICES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1092
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Underhood thermal management: Temperature and heat flux measurements and physical analysis
Khaled, Mahmoud
Harambat, Fabien
Peerhossaini, Hassan
Aerodynamic cooling drag, caused by car underhood cooling, can be reduced by better underhood aerothermal management. This study addresses the aerothermal phenomena encountered in the vehicle underhood compartment by physical analysis of the heat transfer modes in complex internal flows. We report here underhood heat flux and temperature measurements on a vehicle in wind tunnel S4 of Saint-Cyr-France using a new experimental method. The underhood is instrumented by 40 surface and air thermocouples and 20 fluxmeters. Measurements are carried out for three thermal functioning points: the engine in operation and the front wheels positioned on the test facility with power-absorption-controlled rollers. The ultimate aim is to reengineer the underhood architecture so as to reduce the cooling air flow rate in the underhood component and hence the aerothermal cooling drag. (C) 2009 Elsevier Ltd. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/90
info:doi/10.1016/j.applthermaleng.2009.11.003
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1093
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Eddy Heat Transfer by Secondary Goumlrtler Instability
Momayez, L.
Delacourt, G.
Dupont, P.
Peerhossaini, H.
Experimental measurements of flow and heat transfer in a concave surface boundary layer in the presence of streamwise counter-rotating Goumlrtler vortices show conclusively that local surface heat-transfer rates can exceed that of the turbulent flat-plate boundary layer even in the absence of turbulence. We have observed unexpected heat-transfer behavior in a laminar boundary layer on a concave wall even at low nominal velocity, a configuration not studied in the literature: The heat-transfer enhancement is extremely high, well above that corresponding to a turbulent boundary layer on a flat plate. To quantify the effect of freestream velocity on heat-transfer intensification, two criteria are defined for the growth of the Goumlrtler instability: P(z) for primary instability and P(rms) for the secondary instability. The evolution of these criteria along the concave surface boundary layer clearly shows that the secondary instability grows faster than the primary instability. Measurements show that beyond a certain distance the heat-transfer enhancement is basically correlated with P(rms), so that the high heat-transfer intensification at low freestream velocities is due to the high growth rate of the secondary instability. The relative heat-transfer enhancement seems to be independent of the nominal velocity (global Reynolds number) and allows predicting the influence of the Goumlrtler instabilities in a large variety of situations.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/91
info:doi/10.1115/1.4001307
Civil and Environmental Engineering Publications
Scholarship@Western
GROWING BOUNDARY-LAYERS
GORTLER VORTICES
NONLINEAR DEVELOPMENT
TRANSFER ENHANCEMENT
STREAMWISE VORTICES
VORTEX FLOW
GROWTH
BREAKDOWN
ANALOGY
ROLLS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1098
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
ACTIVE CONTROL OF AIR FLOW IN VEHICLE UNDERHOOD COMPARTMENT-TEMPERATURE AND HEAT FLUX ANALYSIS
Khaled, Mahmoud
Harambat, Fabien
Yammine, Anthony
Peerhossaini, Hassan
An experimental analysis of the aerothermal phenomena in the vehicle underhood is given using temperature measurements and separate measurements of convective and radiative heat fluxes. The vehicle underhood used for these measurements is instrumented by 120 surface and air thermocouples and 20 fluxmeters. Measurements are carried out on a passenger vehicle in wind tunnel S4 of Saint-Cyr-France for three thermal functioning conditions. In particular, it is shown for some components that outside air entering the engine compartment (for cooling the different components by convection) can in fact heat other components. This problem results from the underhood architecture, specifically the positioning of some components downstream of warmer components in the same airflow. To avoid this undesired situation, an optimized thermal management procedure is proposed that uses static and dynamic air deflectors during the constant-speed driving (rooting) phase of a vehicle. Much of the present paper is devoted to fluxmetric analysis of underhood thermal behavior (especially the absorption of convective heat flux); we also describe a new control procedure for implementing air deflectors in the actual car underhood.
2010-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/96
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1101
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
AERODYNAMIC FORCES ON A SIMPLIFIED CAR BODY - TOWARDS INNOVATIVE DESIGNS FOR CAR DRAG REDUCTION
Khaled, Mahmoud
Harambat, Fabien
Yammine, Anthony
Peerhossaini, Hassan
The present paper exposes the study of the cooling system circulation effect on the external aerodynamic forces. We report here aerodynamic force measurements carried out on a simplified vehicle model in wind tunnel. Tests are performed for different airflow configurations in order to detect the parameters that can affect the aerodynamic torsor and to confirm others previously suspected, especially the air inlets localization, the air outlet distributions and the underhood geometry. The simplified model has flat and flexible air inlets and several types of air outlet, and includes in its body a real cooling system and a simplified engine block that can move in the longitudinal and lateral directions. The results of this research are generic and can be applied to any new car design. Results show configurations in which, with respect to the most commonly adopted underhood geometries, the overall drag coefficient can be decreased by 2%, the aerodynamic cooling drag coefficient by more than 50% and the lift coefficient by 5%. Finally, new designs of aerodynamic drag reduction, based on the combined effects of the different investigated parameters, are proposed.
2010-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/99
Civil and Environmental Engineering Publications
Scholarship@Western
WIND
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1104
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Pulsating Flow for Mixing Intensification in a Twisted Curved Pipe
Timite, B.
Jarrahi, M.
Castelain, C.
Peerhossaini, H.
This work concerns the manipulation of a twisted curved-pipe flow for mixing enhancement. Previous works have shown that geometrical perturbations to a curved-pipe flow can increase mixing and heat transfer by chaotic advection. In this work the flow entering the twisted pipe undergoes a pulsatile motion. The flow is studied experimentally and numerically. The numerical study is carried out by a computational fluid dynamics (CFD) code (FLUENT 6) in which a pulsatile velocity field is imposed as an inlet condition. The expert. mental setup involves principally a "Scotch-yoke" pulsatile generator and a twisted curved pipe. Laser Doppler velocimetry measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bends during the pulsation phase. These measurements were made for a range of steady Reynolds number (300 <= Re-st <= 1200), frequency parameter (1 <= alpha = r(0).(omega/upsilon)(1/2) <20), and two velocity component ratios (beta = U-max,U-osc/U-st. We observe satisfactory agreement between the numerical and experimental results. For high beta, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter a increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. Experimental results also show that pulsating flow through a twisted curved pipe increases mixing over the steady twisted curved pipe. This mixing enhancement increases with beta. [DOI: 10.1115/1.4000556]
2009-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/102
info:doi/10.1115/1.4000556
Civil and Environmental Engineering Publications
Scholarship@Western
CHAOTIC ADVECTION
HEAT-TRANSFER
LAMINAR-FLOW
VISCOUS-FLOW
VELOCITY
PRESSURE
REGIME
TUBES
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1108
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Fluid flow and convective heat transfer in flat microchannels
Mokrani, Omar
Bourouga, Brahim
Castelain, Cathy
Peerhossaini, Hassan
This study investigates the design, construction and instrumentation of an experimental microchannel, with a rectangular cross-section and large aspect ratio, that allows characterization of the flow and convective heat transfer under well defined and precise conditions and makes it possible to vary the hydraulic diameter of the microchannel. The flow friction coefficient is estimated by direct pressure drop measurements inside the microchannel in a zone where the flow is fully developed. Since the wall thermal conditions inside the microchannel can not be measured directly, their estimation requires temperature measurements in the wall thickness and an inverse heat conduction method. The thermal and hydrodynamic results obtained by varying the hydraulic diameter between 1 mm and 100 mu m do not deviate from the theory or empirical correlations for large-scale channels, These results let us confirm that for smooth walls the continuum mechanics laws for convection and fluid mechanics remain valid in microchannels of hydraulic diameter greater than or equal to 100 mu m. (C) 2008 Elsevier Ltd. All rights reserved.
2009-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/106
info:doi/10.1016/j.ijheatmasstransfer.2008.08.022
Civil and Environmental Engineering Publications
Scholarship@Western
FORCED-CONVECTION
PRESSURE-DROP
RECTANGULAR MICROCHANNELS
SILICON MICROCHANNELS
CHANNELS
WATER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1086
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Turbulent mixing and residence time distribution in novel multifunctional heat exchangers-reactors
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Multifunctional heat exchanger-reactors show significant promise in increasing the energy efficiency of industrial chemical processes The performance of these systems is conditioned by flow properties and is strongly geometry dependent Here CFD simulation and laser Doppler anemometry (LDA) measurements are used to investigate the redistributing effects of the longitudinal vorticity generated by rows of inclined trapezoidal tabs on turbulent mixing in static mixers Studies are carried out on three different configurations in the first the tabs are aligned and inclined in the direction of flow (the reference geometry for a high-efficiency vortex (HEV) static mixer) in the second a periodic 45 tangential rotation is applied to the tab arrays with respect to one another and in the third the reference geometry is used in the direction opposite to the flow direction (reversed direction) The mixing efficiency taken as the resultant of the momentum-transfer efficiency of the mean flow at different scales is studied Macro-mixing entails the dispersive capacity of the flow at the heat exchanger-reactor scale and is generally measured by the residence time distribution (RTD) At the intermediate scale meso-mixing is governed by the turbulent fluctuations this process of turbulent mixing can be characterized by the turbulence kinetic energy (TKE) Micro-mixing is characterized by the local rate of turbulence energy dissipation and is related to the progress of fast chemical reactions and selectivity It is shown here that the reversed-array arrangement (the third configuration) provides the best performance in micro- (50%) and meso-mixing (25%) but exhibits an approximately 40% increase in power consumption over the classical HEV (reference) geometry and somewhat pronounced bimodal behavior in the RTD (C) 2010 Elsevier B V All rights reserved
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/84
info:doi/10.1016/j.cep.2010.08.007
Civil and Environmental Engineering Publications
Scholarship@Western
2 IMMISCIBLE FLUIDS
STATIC MIXERS
FLOW
TAB
AUGMENTATION
GENERATORS
VORTICES
CLOSURE
MASS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1087
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Pulsatile viscous flow in a curved pipe: Effects of pulsation on the development of secondary flow
Timite, Brahim
Castelain, Cathy
Peerhossaini, Hassan
This work presents an experimental and numerical study of pulsated Dean flow, three-dimensional pulsatile flow in a curved pipe. The numerical study is performed by CFD code (Fluent 6) in which a pulsated velocity field is imposed as an inlet condition. The experimental setup involves principally a "Scotch-yoke" pulsatile generator and a 90 degrees bend. Laser Doppler Velocimetry (LDV) measurements have shown that the Scotch-yoke generator produces pure sinusoidal instantaneous mean velocities with a mean deviation of 3%. Visualizations by laser-induced fluorescence (LIF) and velocity measurements, coupled with the numerical results, have permitted analysis of the evolution of the swirling secondary flow structures that develop along the bend during the pulsation phase. These measurements were made for a range of stationary Reynolds number (300 <= Re-st <= 1200), frequency parameter (1 <= alpha = r(0) (omega/v)(1/2) <20), and two velocity components ratios beta = U-max,U-osc/U-st). We observe satisfactory agreement between the numerical and experimental results. For high beta, the secondary flow structure is modified by a Lyne instability and a siphon effect during the deceleration phase. The intensity of the secondary flow decreases as the parameter a increases during the acceleration phase. During the deceleration phase, under the effect of reverse flow, the secondary flow intensity increases with the appearance of Lyne flow. (c) 2010 Elsevier Inc. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/85
info:doi/10.1016/j.ijheatfluidflow.2010.04.004
Civil and Environmental Engineering Publications
Scholarship@Western
WALL SHEAR-STRESS
CHAOTIC ADVECTION
LAMINAR-FLOW
FLUID
TUBES
STENOSIS
NUMBER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1085
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Ice slurry crystallization based on kinetic phase-change modeling
Chegnimonhan, V.
Josset, C.
Peerhossaini, H.
Most crystallization models for ice slurries are based on the equilibrium thermodynamic approach, an assumption that is not made a priori here. We present results of simulations grounded on classical nucleation theory and crystal growth included in global Nakamura-type kinetics coupled with the one-dimensional nonlinear heat equation, another way to model the phase change. The work focuses on ice slurry crystallization using kinetic tools integrating the temperature glide for mixtures (i.e., the solid liquid equilibrium temperature T-f depends on the residual fluid's solute concentration) without any equilibrium assumption. The heat-transfer phenomena in the experimental device are first determined, and then the parameters of kinetic function of crystallization are identified for pure water samples and then for 15 wt% monopropylene glycol (MPG) - water mixtures. An inverse method is implemented with a genetic algorithm to determine the kinetic parameters. (C) 2010 Elsevier Ltd and IIR. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/83
info:doi/10.1016/j.ijrefrig.2010.06.006
Civil and Environmental Engineering Publications
Scholarship@Western
NONISOTHERMAL CRYSTALLIZATION
AQUEOUS-SOLUTIONS
POLYMER
ENERGY
WATER
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1090
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Flow structure and heat transfer induced by embedded vorticity
Kaci, Hakim Mohand
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Several vortex generator shapes are used to increase heat and mass transfer in open and internal flows. Here we report a three-dimensional numerical study investigating the effects of longitudinal and transverse vortices on the heat and mass transfer mechanisms generated by rows of trapezoidal vortex generators. The turbulent macrostructures of these streamwise vortices appear greatly to enhance radial convective transfer. Due to Kelvin-Helmholtz instability, the shear layer shed from the tab's edge becomes unstable and generates periodic transverse vortices that enhance fluid mixing and heat transfer. A global performance analysis of the high-efficiency vortex (HEV) heat exchanger designed to exploit these embedded vortices, shows that the HEV is very competitive with other multifunctional heat exchangers/reactors, especially due to its very low energy consumption. (C) 2010 Elsevier Ltd. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/88
info:doi/10.1016/j.ijheatmasstransfer.2010.04.029
Civil and Environmental Engineering Publications
Scholarship@Western
GORTLER INSTABILITY
TRANSFER ENHANCEMENT
STREAMWISE VORTICITY
CHANNEL FLOW
STATIC MIXER
MIXING TAB
EXCHANGERS
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1094
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
The Dean instability in power-law and Bingham fluids in a curved rectangular duct
Fellouah, H.
Castelain, C.
Ould-El-Moctar, A.
Peerhossaini, H.
The laminar flow of power-law and yield-stress fluids in 180, curved channels of rectangular cross section was studied experimentally and numerically in order to understand the effect of theological fluid behavior on the Dean instability that appears beyond a critical condition in the flow. This leads to the apparition of Dean vortices that differ from the two corner vortices created by the channel wall curvature. Flow visualizations showed that the Dean vortices develop first in the near-wall zone on the concave (outer) wall, where the shear rate is higher and the viscosity weaker; then they penetrate into the centre of the channel cross section where power-law fluids have high viscosity and Bingham fluids are unyielded in laminar flow. Based on the complete formation on the concave wall of the new pairs of counter-rotating vortices (Dean vortices), the critical value of the Dean number decreases as the power-law index increases for the power-law fluids, and the Bingham number decreases for the Bingham fluids. For power-law fluids, a diagram of critical Dean numbers, based on the number of Dean vortices formed, was established for different axial positions. For the same flow conditions, the critical Dean number obtained using the axial velocity gradient criterion was smaller then that obtained with the visualization technique. (C) 2009 Elsevier B.V. All rights reserved.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/92
info:doi/10.1016/j.jnnfm.2009.10.009
Civil and Environmental Engineering Publications
Scholarship@Western
HERSCHEL-BULKLEY FLUID
NEWTONIAN FLUIDS
FLOW DEVELOPMENT
LAMINAR
EXPANSION
ONSET
PIPE
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1096
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Temperature and Heat Flux Behavior of Complex Flows in Car Underhood Compartment
Khaled, Mahmoud
Harambat, Fabien
Peerhossaini, Hassan
In this work heat transfer and temperature behavior of complex flows encountered in the vehicle underhood compartment is experimentally studied and described with simple models. Underhood thermal measurements made on a passenger vehicle in a large-scale wind tunnel are reported here. The underhood is instrumented by 80 surface and air thermocouples and 20 fluxmeters. Measurements are carried out at three thermal functioning points, in all of which the engine is in operation and the front wheels are positioned on the test facility with power-absorption-controlled rollers. Models are proposed to predict the maximum temperatures and time constants of the underhood components as functions of the car speed and car engine power. The relative errors of the models are 3.6% and 3.7%, respectively. The maximum temperature and the time constant are crucial in the design and optimization of the underhood aerothermal management system. The results obtained in the present work also provide a large database for validation of numerical codes dealing with underhood cooling management.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/94
info:doi/10.1080/01457631003640321
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1097
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
Turbulence behavior of artificially generated vorticity
Habchi, Charbel
Lemenand, Thierry
Della Valle, Dominique
Peerhossaini, Hassan
Longitudinal vortices and hairpin-like structures are generated in an open loop flow by a row of vortex generators inserted on the inner wall of a circular pipe; the vortex generator row is made up of four diametrically opposed trapezoidal tabs tilted from the wall. Steady counter-rotating vortex pairs and periodic hairpin-like structures develop downstream from each tab. The flow pattern of these vortical structures has been studied extensively [D. Dong and H. Meng, Flow past a trapezoidal tab, J. Fluid Mech. 510 (2004), pp. 219-242]; nevertheless, the specific contributions of these structures to the mixing process have not yet been elucidated, especially with regard to global improvement of the transfer coefficients compared to a straight pipe. This study aims at exploring the turbulent mixing mechanisms caused by artificially generated vorticity, especially at the different mixing scales (macro-, meso- and micro-mixing), using both numerical simulations and laboratory experiments. Instantaneous velocities and spectral analysis using Laser Doppler Velocimetry are carried out for axial velocity components. Numerical simulations using the Reynolds stress turbulence model are also performed to investigate the effect of the different flow structures on the averaged Reynolds stress tensor and the turbulent kinetic energy dissipation rate. The development and decay of the counter-rotating vortices are also investigated using a recent pseudo-viscous model [O. Logdberg, J.H.M. Fransson, and P.H. Alfredsson, Streamwise evolution of longitudinal vortices in a turbulent boundary layer, J. Fluid Mech. 623 (2009), pp. 27-58]. Here we modify this model to predict the center path of the streamwise vortices in a turbulent boundary layer. It is also shown that the hairpin-like structures govern both meso- and micro-mixing mechanisms, while the counter-rotating vortices act as internal agitators in the flow by creating convective transfer between the wall region and the flow core. This investigation is fundamental for optimizing static mixers based on vortex generators and for control of separation in aerodynamic applications.
2010-01-01T08:00:00Z
article
https://ir.lib.uwo.ca/civilpub/95
info:doi/10.1080/14685248.2010.510841
Civil and Environmental Engineering Publications
Scholarship@Western
HEAT-TRANSFER ENHANCEMENT
2 IMMISCIBLE FLUIDS
GORTLER INSTABILITY
FLOW STRUCTURE
WALL TURBULENCE
BOUNDARY-LAYER
CHANNEL FLOW
MIXING TAB
VORTEX
AUGMENTATION
Materials Science and Engineering
oai:ir.lib.uwo.ca:civilpub-1100
2019-02-13T17:18:08Z
publication:civil
publication:faculties
publication:civilpub
FLUXMETRIC ANALYSIS OF CAR INCLINATION EFFECTS ON THE THERMAL MANAGEMENT OF UNDERHOOD TOP REGION
Khaled, Mahmoud
Harambat, Fabien
Hamadi, David
Yammine, Anthony
Peerhossaini, Hassan
It is now well established that car inclination influences component temperatures in the car underhood compartment [1, 2]. This study presents an analysis of these effects by measurement of the heat flux that enters or leaves the underhood components. We report underhood thermal measurements carried out in wind-tunnel S4 of Saint-Cyr l'Ecole on a passenger vehicle. The underhood compartment is instrumented with 40 surface and air thermocouples and 20 fluxmeters of normal gradients. Three configurations of car positions are investigated: the flat, the up-hill and the down-hill inclinations. Measurements are can-led out for three different car thermal functioning points.
2010-01-01T08:00:00Z
conference
https://ir.lib.uwo.ca/civilpub/98
Civil and Environmental Engineering Publications
Scholarship@Western
Materials Science and Engineering
878208/oai_dc/100//