Doctor of Philosophy
Mechanical and Materials Engineering
Straatman, Anthony G.
Porous media prevail in industry e.g. heat transfer equipment, drying, food storage and several other applications. Integrated in engineering, they form conjugate Fluid/Porous domains. Physical modelling requires characterizing the microscale heat and mass (moisture) transfer interstitially within porous media and their macroscale counterparts across regional interfaces. Characterizing turbulence and its effects on phase coupling is often needed too. The modeling literature survey shows phase coupling assumptions depending on empiricism, phase equilibrium and lack of generality. Modeling of the dynamic variations for the modes of phase exchanges, i.e. heat, mass and heat accompanying mass exchanges, on both scales and generic turbulent coupling across fluid/porous interfaces are absent. Thus, the objectives of this thesis are to, i) develop a dynamic coupling model for phase heat and mass transfer in conjugate fluid/porous domains, ii) validate the model in terms of interstitial phase exchange, macroscopic interfaces and behaviors in different modes of heat and mass transfer, iii) extend the model to turbulent flows characterizing turbulence correctly for different porosities and permeabilities. The modeling process depends on a finite volume approach. Continuity, momentum, turbulence, energy and mass equations are solved in point form for fluid regions. In porous media, a volume averaged version is formulated and solved using one equation per phase e.g. fluid temperature, solid temperature, vapor in fluid mass fraction and liquid in liquid/solid mixture mass fraction. Mathematical conditions are utilised at macroscopic interfaces reconciling the point-volume form differences, to ensure continuity of conservation variables and numerical robustness. Physical phase exchange formulae and numerical implementations for macroscopic interface heat/mass and turbulence treatments are introduced. The model is validated interstitially by comparing to experiments of Coal particles drying, for macroscopic coupling by comparing to experiments and other models of apple and mineral plaster drying, respectively. The results showed good agreement for all the cases. The turbulent coupling model has been tested for a channel with porous obstruction high and low permeability cases and compared well to other studies in the literature. Finally, full turbulent flow, heat and mass transfer was tested and produced physically correct trends and contours for apple and potato slices drying.
Elhalwagy, Mahmoud Mohamed Mostafa, "Dynamics of the Phase Coupling for Flow, Heat and Mass Transfer in Conjugate Fluid/Porous Domains" (2018). Electronic Thesis and Dissertation Repository. 5437.