Modeling of the drying process of apple slices: Application with a solar dryer and the thermal energy storage system

Abstract

In this study a solar air heater was developed to determine the drying rate of apple (Golden Delicious). In order to provide the drying process continuously a packed bed thermal energy storage system was designed and manufactured. Also, a recuperator unit was used for waste heat recovery. In the recuperator unit, it is provided the mixing of the fresh air with the drying air whose moisture content increases, at a specified rate. So at the rate of 50–60% waste heat is recovered and reutilized in the drying system. The advantage of the system is that it consumes less energy at the rate of 76.8% than other drying technologies. Experiments on the drying system were repeated twice a day. In the experiments the drying kinetics of apple slices (5 ± 2 mm thick) was determined at constant temperatures ranging from 50−60°C. Also, Diffusion Approximation model was used for drying of apple slices in constant temperature. A mathematical model was developed to calculate the prediction of the moisture ratio during time and it is observed that the model is complied with the studies in the literature.