MODELING OF DIFFUSION IN CAPILLARY-POROUS MATERIALS DURING THE DRYINGPROCESS

This paper presents a model of heterogenous diffusion in capillary por ous materials during the process of drying. The governing heat and mas s transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by conside ring the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the mois ture and temperature dependent thermophysical properties of the produc t. All equations have been established in spherical coordinates but th e programme written for the purpose of calculations can be used for ot her geometries also. Numerical calculations have been performed for ga s concrete and tiles using model 1, while model 2 has been used for ga s concrete only because of the lack of data for thermophysical propert ies of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions o f the drying process were reasonably accurate.