Heat Transfer in Porous Media. Conduction, Convection, Radiation Heat Transfer

A porous medium is a complex-shaped solid containing cavities called pores. These cavities can communicate with each other and contain one or more fluid phases that can flow and, if necessary, exchange matter and/or energy with each other and/or with the solid. The solid part, also known as the porous matrix, may be deformable but must have a certain cohesion, which excludes from our definition fluidized beds made up of solid particles held in suspension under the effect of an interstitial fluid flow.

Numerous examples of porous media can be found in everyday life: textiles, leather, paper, fabrics, building materials, insulation, soil and rock formations, filters, heat exchanger coatings, dehydrated food and vegetables, biological fabrics, nuclear reactors, chemical engineering columns, and so on.

They vary enormously in structure (shape and size of matrix grains and pores), nature (physico-chemical properties of constituent materials) and spatial scale (from tens of cubic kilometers for hydrocarbon deposits and groundwater to a few cubic millimeters for certain types of filter membrane).

Porous media play an important role in many industrial sectors and natural phenomena. Typical examples include: petroleum engineering, chemical engineering and electrochemistry, hydrogeology, geothermal engineering, thermal engineering, civil engineering, medicine, biochemistry, nuclear engineering...

Porous media are the seat of multiple physico-chemical and transport phenomena. The study of these phenomena requires knowledge of the storage properties of fluids (either in adsorbed form on the solid, or filling the pores), transfer properties (mass, momentum, energy) and possibly mechanical properties. As with all multiphase heterogeneous systems, these properties are obviously a function of matrix morphology and the phenomena that develop and interact in the different phases, making the field of heat transfer studies in porous media particularly vast. For this reason, the elements developed here and in the following article [BE 8 251] , which deals with heat transfer with phase change, do not claim to exhaust the subject. After introducing the essential concepts of porous media characterization, they are simply intended as a synthesis and introduction to more specialized works.