Performance analysis of a secondary heat recovery solar-assisted heat pump drying system for mango

An experimental investigation of solar-assisted heat pumpa drying mango has been conducted. A new solar-assisted heat pump drying system with a secondary heat recovery was setup, which can operate independently in solar drying mode and heat pump drying mode, or operate in a joint mode. An evaporator of the heat pump and a heat exchanger were adopted to recover the waste heat from the exhaust moist air from the drying chamber for increasing the utilization of energy. The mango slices of 80 kg were spread over 40 trays in the form of a single layer for the drying test with the hot air of 45°C. The experiments were conducted to dry the mango with solar drying mode and heat pump drying mode for studying the performance of the new drying system. The time durations were 6.5 h with the solar drying mode and 10.7 h with the heat pump drying mode for drying the mango, respectively. Moreover, the efficiency of the solar-assisted drying mode was 6% higher than the heat pump drying mode and the power consumption of 3.5 kW h could be saved by using the solar-assisted heat pump mode. The coefficients of performance were 3.48 and 3.69 for the heat pump drying mode and the solar-assisted heat pump mode, respectively. The average efficiency of the heat exchanger for recovering the waste heat could reach 41.7% during the whole working process.