Experimental investigation of the effect of heat pump drying temperature on drying characteristics of Auricularia auricula

To effectively improve the quality of dried Auricularia auricula and reduce drying energy consumption, based on a designed heat pump experimental device, the impacts of drying temperature as a critical factor, on the drying characteristics of Auricularia auricula and the performance of the heat pump system as well were investigated experimentally. The results show that, within the drying temperature range of 40–65 °C, as the drying temperature increases, the decrease in the moisture ratio (MR) becomes more pronounced. Drying time decreases from 495 min to 255 min, with an average drying rate (DR) increasing by 93.8 %. The average coefficient of performance of the system (COP_sys) decreases by 14.9 %, the average specific moisture extraction rate (SMER) and the rehydration ratio (R_f) both initially increases and then decreases. At a drying temperature of 55 °C, the average SMER reaches its maximum value at 0.74 kg/kWh, indicating the optimal dehumidification performance for the system. Meanwhile, at a drying temperature of 50 °C, R_f for Auricularia auricula reaches its maximum value at 14.16, signifying the optimal quality of Auricularia auricula. Compared to hot air drying, the heat pump drying (HPD) system demonstrates lower energy consumption and superior economy, while also yielding higher-quality Auricularia auricula. The findings can provide valuable insights into the employment of heat pump drying system in the drying process of Auricularia auricula.