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. Experinients 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 degrees 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. (C) 2017 Elsevier Ltd. All rights reserved.