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Non-dilute salt strength solutions occur in many near surface geologic environments. In order to better understand the occurrence and movement of the water and salt, mathematical models for this non-ideal fluid need to be developed. Initial boundary value problems may then be solved to predict behavior for comparison with observations. Using the principles of equilibrium reversible and irreversible thermodynamics, relationships describing the thermo-physics of non-dilute saline solutions in variably saturated porous media are investigated. Each of four central chapters investigates a particular aspect of the flow of saline solutions through porous media. The first chapter derives the general relationships describing the effects of salt on the vapor content in the gas phase and also on the liquid pressure. The second chapter summarizes an example using the new theory for sodium chloride (NaCl) from zero to saturated strength. Additional terms beyond the dilute approximation are shown to be more important in very dry, fine textured soils with significant salt content. The third chapter derives the salt corrections for Darcy-type flow laws for variably saturated porous media, and an example for NaCl is given. Agreement between theory and experimental data is good, though there appear to be some unaccounted for effects. These effects may be the result of ionic interaction of the salt with the loamy sand used, and/or the effect of hysteresis of the water content-pressure relationship. The final chapter investigates two fundamental assumptions commonly used in process thermodynamics when considering mixtures described by porous media, saline water, and moist air. The first assumption is that temperature is the generalized intensive variable associated with entropy. The second assumption is that the form of the differential of total energy is known a-priori. It is shown that the first assumption is suspect under some circumstances, and a generalized notion of how to select extensive variables for a given system is introduced for comparison with the second assumption. Examples comparing the "usual" and new theories are accomplished for ideal gases and for isotropic Newtonian liquids, with results being favorable except possibly for the Gibbs-Duhem Relation of the Newtonian liquid for the "usual" theory. / Graduation date: 2005

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Thesis (MScEng)--University of Stellenbosch, 2002 / ENGLISH ABSTRACT: A Representative Unit Cell (RUC) model for flow through two-dimensional porous media is presented and applied to two industrial related problems. The first application is to that of cross-flow in tube banks. Both staggered and square (inline) configurations are investigated and the model results are compared to experimental data. The second application is to flow through a stack in a timber-drying kiln. The RUC model is applied to the anisotropic timber stack ends and the centre part is modelled with a standard duct flow solution. The results of the models applied to a timber stack are compared to experimental data obtained from model tests undertaken in a wind tunnel. The results of the RUC and duct flow models are found to be in excellent agreement with the data of the experimental models. These models may be used to optimize kiln designs. / AFRIKAANSE OPSOMMING: 'n Verteenwoordigende Eenheid Sel (VES) model vir vloei deur twee-dimensionele poreuse media word weergegee en toegepas op twee industriële toepassings. Die eerste toepassing is op dwarsvloei deur banke van buise. Beide gestapelde en inlyn konfigurasies word ondersoek waarvan die model resulte met eksperimentele data vergelyk word. Die tweede toepassing is op vloei deur 'n stapel in 'n hout-droogoond. Die VES model word toegepas op die anisotropiese ente van houtstapels en die middelste seksie word gemodelleer deur 'n standaard kanaalvloei oplossing. Die resultate van die modelle toegepas op n 'houtstapel word vergelyk met eksperimentele data verkry uit model toetse wat in 'n wind-tonnel uitgevoer is. Die VES en kanaalvloei modelle se resultate stem uitstekend ooreen met die data van die eksperimentele modelle. Hierdie modelle kan gebruik word om die ontwerp van droogoonde te optimeer.