Research into technological process of convective fruit drying in a solar dryer

Abstract

We proposed a generalized procedure of convective fruit drying, which takes into account comprehensive combination of thermal-physical and physical-chemical properties of fruit with their kinematic heat and mass exchange characteristics. We developed a mathematical model of heat, moisture and mass exchange for convective fruit drying, which considers moisture-yielding velocity of the dried material in the operation zone of the heat carrier under conditions of diffusion process of moisture transfer in the dried material. The given model allows us to determine heat and mass exchange characteristics and intensity of the drying process. We proposed the systems of differential equations of heat and moisture transfer in the process of convective fruit drying for parabolic and uniformed original distribution of temperature and moisture content. As a result of the solution of a system of differential equations, we obtained appropriate dependences to determine the energy of bound moisture, moisture content on the surface and in the center of the material, difference of moisture content between the surface and central layers, as well as critical moisture content. The obtained results may be used when predicting the heat and mass exchange processes, for improvement of technology and equipment for fruit drying in the solar dryer, for increasing technological and energy efficiency of the process.