Study on Optimal Operation of Heat Pump Drying System Throughout the Entire Drying Process Based on the Material Drying Characteristics

This study investigates the application of Heat Pump Drying (HPD) technology for drying agricultural products, aiming to address the practical inefficiency of HPD systems, which stems from the lack of an optimized operational strategy throughout the drying process. This study develops a mathematical model for a closed-loop HPD system. Tomato slices were selected as the research subject, and hot air-drying experiments were performed to determine their drying characteristics. The mathematical model was then used to simulate the effect of material moisture content fluctuations on HPD system performance during drying. Based on these drying characteristics, an optimal operational strategy was proposed. The results show that dynamically adjusting parameters such as evaporation temperature and air bypass ratio during different drying stages can significantly improve the system’s Specific Moisture Extraction Rate (SMER) and facilitate energy-efficient operation throughout the drying process. The average SMER values of the HPD system under the optimized strategy were 2.59 kg∙kW⁻¹∙h⁻¹ and 3.46 kg∙kW⁻¹∙h⁻¹ at drying temperatures of 60 °C and 80 °C, respectively. Additionally, the optimized operation reduced total electrical consumption by 31.60% and 32.87% compared to the constant evaporation temperature mode.