Comparative and comprehensive experimental analysis: Performance variation of a novel hybrid dryer

Abstract

Conventional energy sources are integrated into solar dryers to allow them to operate day and night. Unlike previous applications, this work presents a novel hybrid dryer in which an external geothermal heat exchanger unit is integrated into an indirect solar dryer to overcome this problem. The tomato drying performance of the hybrid dryer was compared with a solar dryer and conventional shade drying in simple and ventilated modes. The proposed dryer's energy, exergy, and economic performance were evaluated using solar and geothermal energy. During the same period, the hybrid dryer reduced the samples to at least 3.64 times lower moisture content in simple mode than other dryers. In ventilated mode, this value was 2.97 times. Integration of ventilation into the hybrid dryer reduced average drying time from 64 to 56 h, specific moisture extraction rate from 0.63 to 0.60 kg/kWh, specific energy consumption from 3.94 to 2.78 kWh/kg, and payback time from 0.22 to 0.17 years. However, it increased the thermal and exergy efficiency of both dryers' solar air collectors by over 30 % and 27 %, respectively. As a result, the hybrid dryer continued the drying process even when there was no sun and achieved a significant advantage in drying tomatoes compared to the other two drying types. The proposed system will make locations where geothermal energy is available attractive for food drying.