Performance of a desiccant assisted packed bed passive solar dryer for copra processing

In this paper, the performance of a novel desiccant assisted packed bed passive solar dryer was evaluated for copra processing and compared with conventional passive solar dryer. This novel solar dryer consists of a desiccant assisted packed bed solar air heater attached with a dryer cabin. The desiccant and phase change materials packed in the solar air heater has control the humidity and retains the heat for longer duration, respectively. The performance of the dryer was evaluated (in terms of drying time to attain the final equilibrium moisture content, drying rate, specific moisture extraction rate, pick-up efficiency, and dryer efficiency) under the meteorological conditions of Coimbatore city in India during March and April 2016. The copra was dried from initial moisture content (wet basis) of about 52% to the final moisture content (wet basis) of about 8% in 62 hours with specific moisture extraction rate of 0.82 kg/kWh. The drying time was reduced by about 44 hours when compared to the conventional passive solar dryer. The dryer pick-up efficiency was varied between about 10% and 65%. The average dryer thermal efficiency was calculated to be about 32%. The quality of final dried product was found to be good.