Natural convection in a fluid layer is a phenomenon which has been the topic of numerous studies. A similar phenomenon has been observed in porous media. In the first part of this paper we review some recent theoretical and experimental studies which allow a better understanding of some quantitative aspects of natural convection in porous media. This review is confined to the case in which compressibility effects are negligible as compared to thermal expansion effects and where the porous layer is homogeneous. Some results are presented on natural convection in a horizontal layer with different types of boundary conditions and in a sloped layer bounded by isothermal planes. Some aspects of mixed convecti on are also discussed.The second part of the paper is concerned with prac-tical cases. As a major example we give the description of natural convection occurring in the Lacq gas reservoir. We also present some examples of oil production operations where thermal convection may have an influence. These may be classified into two categories: (a) convective motions already existing in a reservoir and having an influence on the handling of the recovery methods; (b) convective motion induced by the recovery technique itself (thermal methods). Finally we discuss the case of thermal convection in aquifers, with special reference to the understanding of geothermal areas. INTRODUCTION NATURAL (or free) thermal convection in a fluid layer is a physical phenomenon which has been the topic of numerous studies {1,6,11,25). When in a fluid phase the vertical component of the temperature gradient has the same direction as gravity, the upper layer of the fluid is heavier than the lower and some motions, called convection motions, may exist. These motions tend to reduce the adverse density gradient.The existence of convective motions in areas of geothermal activity has been known for a long time.The existence of the solid matrix of the porous medium does not mollify in any important manner the qualitative aspects of the phenomenon. This analogy between the fluid layer and the porous medium has been justified by a number of recent studies which have also provided considerable quantitative information [7, 12. 19, 22, 24, 26] . These studies pertain to the case in which compressibility effects are negligible as com-pared ti) the thermal expansion effect and where the porous layer is homogeneous and bounded by parallel planes. The problems considered in this paper are (1) con-vection in horizontal layers, (2) convection in sloped layers and (3) mixed (forced and free,) convection.It is possible to gain a good understanding of the phenomenon for almost all practical cases; however, the direct application of the results to practical prob-lems in a quantitative manner is not always easy. This difficulty is due to the complexity of real boundary conditions, the non-uniformity of a real porous structure and also in some cases, the influence of com-pressibility effects. The practical examples given in this paper tend to show that, in spite...

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A numerical investigation of heat conduction and laminar natural convection in ice-water systems containing porous metal foams, undertaken in the context of computationally convenient two-dimensional steady-state problems, is presented in this thesis. The overall goals of this work are to provide improvements to available cost-effective mathematical models of these phenomena, solve these models numerically, and investigate the influence of the porous metal foam on fluid flow and heat transfer in ice-water systems. The long-term goal (and the motivation for this work) is to contribute to the development of mathematical models and numerical solution methods for simulations of enhanced ice-water seasonal coldstorage systems.The proposed mathematical models are based on the local volume-averaging method. A Darcy-Brinkman-Forchheimer model is used for the momentum equations. For the heat transfer, volume-averaged equations governing two intrinsic phase-average temperature fields are used: one for the metal foam and the other for the water (solid or liquid). The following improvements to available two-temperature models are proposed: novel expressions for the interfacial heat transfer coefficient in both the conduction and convection regimes; and modified effective thermal conductivity models that provide consistency between predictions of one-temperature and two-temperature models in the limit of local thermal equilibrium.A well-established fixed-grid, co-located, finite volume method (FVM) is adapted for the numerical solution of the aforementioned mathematical models. All of the computer simulations are done with rectangular calculation domains, cooled and heated on the opposite side walls, and the adiabatic condition is imposed on the top and bottom walls.The FVM is first validated by the comparing the predicted results to experimental data for steady-state conduction and laminar natural convection in square enclosures containing pure liquid water and ice-water systems (no foam), with temperatures spanning the density inversion point of water. The problem involving natural convection in pure liquid water is solved using a variable-property model (VPM) and also a constant-property model (CPM), with the constant fluid properties evaluated at several reference (or average) temperatures,