Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Prof. A.G. Straatman

Abstract

Heat and mass transfer involving porous media is prevalent in, for example, air-conditioning, drying, food storage, and chemical processing. Such applications require non-equilibrium heat and mass (or moisture) transfer modeling inside porous media in conjugate fluid/porous/solid framework. Moreover, modeling of turbulence and turbulent heat and mass transfer becomes essential for many applications. A comprehensive literature review shows a scarcity of models having such capabilities. In this respect, the objectives of the present thesis are to: i) develop a formulation that simulates non-equilibrium heat and mass transfer in conjugate fluid/porous/solid framework, ii) demonstrate the capabilities of the developed formulation by simulating complex related problems, and iii) extend the developed model to such class of problems that involve turbulence and turbulent heat and mass transfer. To develop the required formulation, we first specify transport equations for each region. In the fluid region, mass, momentum, energy, and water vapour transport equations are solved to model flow and energy of moist air-vapour mixture. The volume-averaged version of these equations form the model for the fluid-constituent of porous media, while the transport equations of energy and water mass fraction are solved inside the solid-constituent of porous media and solid region. Mathematical conditions are developed at all the interfaces to ensure smooth transport of relevant quantities across the interfaces. The developed formulation is demonstrated and validated by simulating the problems of evaporative cooling and convective drying of wet porous materials. In this respect, each simulated case demonstrates critical aspects of the developed formulation. Moreover, the simulated cases are found to be in excellent agreement with experimental data. The developed formulation is extended to turbulent flow regimes often encountered in heat and mass transfer problems related to food stacks. In this respect, the closure is obtained for the macroscopic turbulence and turbulent non-equilibrium heat and mass transfer model inside porous media composed of randomly packed spheres. The closure is obtained by simulating the problem at the pore-level scale of a bed of randomly-packed spheres. Lastly, the closure results are presented in the form of power law-based correlations to be utilized in the macroscopic model.

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