2-D Solution for drying with internal vaporization of anisotropic media



A set of physical assumptions for a straighfforward and eficient simulation of the dying of a porous medium submitted to a conuective and/or radiative heating is proposed. All of the parameters used are physical (liquid migration coefficient, peimeability values along the thickness and the length, thermal conductive, and external exchanges), but the relevant geometrical properties (length and thickness of the slab) were also included in the analysis. The 2-D pressure field generated within the medium during the dying process is obtained by using an analytical expression. The treatment of the pressure field, especially for a strongly anisotropic medium, is an important feature of the model, which allows an analytical model for such a complicated porous medium as wood to be used across a wide range of dying conditions. The computer code developed from the proposed formulation permits a complete simulation of the drying process within a few seconds on a personal computer. Different configurations have been tested for both anisotropic (wood) and isotropic (light concrete) porous media. Agreement with the experimental results is reasonable in terms of the obserued physical phenomena. For instance, the model highlights dependence of the duration of the first diying rate on both material properties and drying conditions. This new model can be used for a global physical characterization of products by curve fitting and the collated information for the design of dryers.