Study of the Performance of an Indirect Forced Convection Solar Dryer Incorporating a Thermal Energy Storage Device on a Granite Bed for Drying Tomatoes

Abstract

Indirect solar dryers combining a solar collector and an enclosure enable the drying process to be run smoothly, with good quality dried products. However, when the process lasts longer than one day, some of the products may be damaged when the drying process is interrupted. The integration of a thermal storage system into indirect solar dryer systems can make up for the unavailability of solar energy and enable the drying process to continue over longer periods without the need for additional energy. With this in mind, the present study investigates the performance of a forced convection indirect solar dryer coupled with a thermal energy accumulator for drying tomatoes. The experiments were carried out with a drying air flow rate of 0.01 kg/s during the drying period. The air flow rate during storage tank charging was 0.013 kg/s. Solar drying performance with and without storage was compared. The results show that to reduce the water content in the dry tomato base from 16.78 kgwater/kgms to 0.125 kgwater/kgms, the indirect solar dryer requires 15 hours of cumulative sunshine spread over two drying days, while the indirect solar dryer coupled with the heat accumulator enables the water content in the dry base to be reduced from 19.81 kgwater/kgms to 0.117 kgwater/kgms over 17 continuous hours, i.e. approximately one sunny day and one night. The overall average efficiency of the indirect solar dryer with heat storage is around 23.31%, compared with 17.47% for the indirect solar dryer.