Heat and mass transfer in wet porous media in presence of evaporation-condensation

The modelling of heat and mass transfer in wet porous media in the presence of evaporation-condensation is revisited by using the homogenization method of asymptotic expansions for periodic structures. In order to produce the 'upscaled' equations for the continuum equivalent to the porous medium, we start from the pore level. At this scale the physics is described by convection and Fick's molecular diffusion coupled with heat transfer. The phase change process is incorporated into the analysis. The main advantage of the method is to use a systematic, rigorous and unified treatment to provide a general comprehension of all the interactions involved by the different heat and mass transfers. Four characteristic selected models are carried out. Their domains of validity are determined in function of the relative weight of the different phenomena in presence. Comparison with other models in the literature is presented. II appears that some of them exhibit a similar structure. In particular, the continuous passage between the different macroscopic models is investigated. Finally, the condition for a non-homogenizable situation, i.e., when it is impossible to find a macroscopic equivalent description is also addressed. (C) 1998 Elsevier Science Ltd. All rights reserved.