Overview
ABSTRACT
Phase change mechanisms are present in many fields: industrial drying operations, geothermal energy, exchangers, … Several macroscopic models are possible: for example Darcean or inertial for the momentum balance, local equilibrium or local non-equilibrium models for the energy balance. Equilibrium water contents depend on capillary and adsorption effects. A complete model is complex. Under certain conditions, a water transport model in the form of a non-linear diffusion equation can be a good approximation. However, the saturation, temperature, concentration, pressure and velocity fields are often complex, reflecting the various mechanisms affecting water transport.
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Read the articleAUTHORS
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Abdelkader MOJTABI: Professor Emeritus - Toulouse Institute of Fluid Mechanics (IMFT), University of Toulouse, CNRS, Toulouse, France
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Marc PRAT: CNRS Research Director Emeritus - Toulouse Institute of Fluid Mechanics (IMFT), University of Toulouse, CNRS, Toulouse, France
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Michel QUINTARD: CNRS Research Director Emeritus - Toulouse Institute of Fluid Mechanics (IMFT), University of Toulouse, CNRS, Toulouse, France
INTRODUCTION
This article, devoted to heat transfer with phase change in porous media, follows on from the article "Heat transfer in porous media. Conduction, convection, radiation"
Phase change phenomena in porous media play an important role in many fields. These include :
exploitation of hydrocarbon deposits. Various thermal methods are used (steam injection, in situ combustion, etc.) which lead to phase change mechanisms;
thermal insulation, which can be severely affected by vapour transfer and condensation;
geothermal energy, transfers between soil and atmosphere ;
multiphase heat exchangers, fuel cells ;
chemical engineering ;
nuclear safety, etc.
Like all multiphase processes, phase change phenomena in porous media are highly complex and, in many respects, our knowledge of them is still only partial. This article looks at the physical processes at work at pore scale and the most common macroscopic models used in drying operations or processes involving boiling.
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KEYWORDS
capillarity | drying | adsorption | water transport model | non-linear diffusion equation
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