Date of Award

1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Abstract

Interferometric and finite difference numerical techniques were employed to study free and mixed convection in open rectangular, semi-cylindrical, and V-shaped isothermal cavities.;An interlocking/overlapping technique was introduced to solve the semi-cylindrical cavity numerical problem.;A Mach-Zehnder interferometer was employed for the experimental free convection, and when integrated with an open circuit low-speed wind tunnel, the interferometer was utilized to study mixed convection.;The parameters within the ranges of Rayleigh number, 10{dollar}\sp3 \leq{dollar} Ra {dollar}\leq{dollar} 5 {dollar}\times{dollar} 10{dollar}\sp5{dollar}, the height to width aspect ratio, 0 {dollar}\leq{dollar} H/W {dollar}\leq{dollar} 1, the angle of inclination, 0{dollar}\sp\circ\leq\alpha\leq60\sp\circ{dollar}, Reynolds number of 380 and 400 and Prandtl number of 0.71 were considered.;For isothermal rectangular cavity there was no distinct conduction regime similar to that observed in cavity heated from the base only, where critical Rayleigh number, Ra{dollar}\sb{lcub}\rm c{rcub}\simeq\ 10\sp3{dollar}. Free convection in isothermal cavity occurred at lower Rayleigh number (Ra {dollar}<{dollar} 10{dollar}\sp3{dollar}). As Ra increased further, air was entrained into the cavity from both sides while the heated air exited through the middle. At Ra = 10{dollar}\sp5{dollar} and 5 {dollar}\times{dollar} 10{dollar}\sp5{dollar}, rolls and secondary rolls were observed in the cavity respectively. When the cavity was inclined at 45{dollar}\sp\circ{dollar}, the entrained cold fluid entered the cavity through the two-thirds of the aperture, and the heated air was deflected upwards as it excited through the remaining one-third. The effect of inclining the cavity at 45{dollar}\sp\circ{dollar} caused about 34% increase in average heat transfer coefficient, Nu{dollar}\sb{lcub}\rm ave{rcub}{dollar}, over the horizontal cavity value.;In mixed convection experiment, the approaching cross-flow of cold air deflected the rising heated air downstream. A distinct shear layer with a dividing streamline isolated the cavity and the deflected plume from the free-stream region. For the parameters considered here, Nu{dollar}\sb{lcub}\rm ave{rcub}{dollar} is about 40% of the value obtained for the case of free convection. For the inclined mixed convection, Nu{dollar}\sb{lcub}\rm ave{rcub}{dollar} is four times the value obtained for the horizontal case.;Correlations were obtained for numerical (horizontal) and experimental (horizontal and inclined) free convection in rectangular cavities. The present results compared favourably with those reported in literature.

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