HEAT AND MASS-TRANSFER MODELING IN AIR-DRYING OF FOODS

Heat and mass transfer modeling in the air drying of solids is considered as a two stage procedure. The former aims to discover the dominant heat and mass transfer phenomena (heat versus mass, internal versus external), the latter aims to formulate empirical equations for the calculation of the corresponding heat and mass transport properties (mass diffusivity, thermal conductivity, boundary heat and mass transfer coefficients). A model discrimination procedure was proposed in the first stage, and a model building procedure was examined in the second stage. The proposed procedures were applied to a wide set of experimental data in potato drying. The resulting model takes into account moisture diffusion and convective heat and mass transfer in the air boundary layer. Moisture diffusivity is dependent an material moisture content and temperature, while heat and mass transfer coefficients can be considered as constants.