Heating Performance, Exergy, and Economic Analysis of a Hpds with an Independent Operating Ability for Drying Shiitake Mushroom

Abstract

A heat pump drying system driven by a gasoline generator with an independent operating ability was proposed to solve the problem of post-harvest drying. The system had two operating modes, namely, heating and dehumidifying modes. The waste heat of air discharged from the drying chamber and gasoline generator was utilized. The heating performance, exergy, and economics of the system were studied using a drying shiitake mushroom by a prototype. Results showed that the drying temperature reached a maximum of 75 °C in heating mode. Meanwhile, the drying air relative humidity rapidly reduced to less than 10% in dehumidifying mode. The exergy destruction and avoidable exergy destruction were higher in gasoline generator, evaporator, condenser, air–air heat exchanger, and exhaust gas heat exchanger, indicating that these components possessed higher improvement potential. The inlet air temperature of the system is 15–20 °C higher when driven by gasoline generator than with electricity. The drying cost of obtaining 1 kg dried mushroom with the gasoline generator is much higher than with electricity due to the low efficiency of gasoline generators and the current energy price. This study provided guidance for the design, operation, and future improvement of the HPDs driven by a generator.

Keywords: heating performance, heat pump drying, operating mode, energy utilization rate, Exergy