MODELING OF COUPLED HEAT AND MASS TRANSFERS WITH PHASE-CHANGE IN A POROUS-MEDIUM - APPLICATION TO SUPERHEATED STEAM DRYING

The physical model is based on balance equations at the representative elementary volume. The considered medium has three phases (liquid, so lid, and gas). The gas phase includes two components (air and vapor) W e use the mass balance equations on air and wafer (liquid and steam) a s wed as the heat equation in order to describe the phenomena. The sys tem of equations lr closed via classical relations in these media, whi ch lends to a three-equation system with coupled nonlinear partial der ivatives. We have applied this model to superheated steam drying. A so lution model of the coupled nonlinear equation system based on the fin ite element method in a two-dimensional configuration was developed an d validated. This approach allows one to determine all the variables o f the problem. It is a complementary tool of analysis that opens acces s to nonmeasurable variables, such as the phase change rate. This comp utation model was applied to a configuration studied experimentally. T he numerical and experimental results agree in nondimensional time. Th is double approach has enabled us to point out and evaluate new mechan isms typical of this drying method.