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, solid, and gas). The gas phase includes two components (air and vapor) We use the mass balance equations on air and wafer (liquid and steam) as wed as the heat equation in order to describe the phenomena. The system of equations lr closed via classical relations in these media, which lends to a three-equation system with coupled nonlinear partial derivatives. We have applied this model to superheated steam drying. A solution model of the coupled nonlinear equation system based on the finite element method in a two-dimensional configuration was developed and validated. This approach allows one to determine all the variables of the problem. It is a complementary tool of analysis that opens access to nonmeasurable variables, such as the phase change rate. This computation model was applied to a configuration studied experimentally. The numerical and experimental results agree in nondimensional time. This double approach has enabled us to point out and evaluate new mechanisms typical of this drying method.