A Semi-Empirical Approach for Predicting the Effects of Shrinkage on the Convective Mass Transfer Evolution During the Solar Drying of Foodstuffs

Abstract

This study analyzes and compares convective mass transfer coefficients: obtained directly from the drying kinetics and considering the theoretical diffusion model, taking into account shrinkage effect. Theoretical analysis allowed obtaining a modified Biot number. The reduction of the wet exchange surface is identified, from measurements of the drying kinetics, shrinkage phenomenon, surface temperature and parameters of dying air. This is the external surface, concerned with the exchanges with drying air. A significant decrease occurs at the beginning of the drying process and tends to a value close to zero when the product is dry. The evolution of convective mass transfer coefficient, during the drying process, can be evaluated. An important drop is observed. The decreasing of the convective mass transfer coefficient, during the drying process of shrinking products, is evaluated.