Performance Simulation of Open-loop Air Cycle Heat Pump Drying System

In contrast with the conventional drying technology, a novel air cycle heat pump drying (ACHPD) system, which uses air as its working medium, is proposed to solve the problems of low energy efficiency and eliminate the use of HCFCs/HFCs. A simulation model is established, and its verification via experimental results from a constructed test bench indicates errors of the drying rate within ±0.01% and the system power within ±7%. Compared with a conventional electric heater drying (EHD) system, the energy-saving rate of the ACHPD system reaches 15%–27% when the water evaporation rate increases from 0.75 kg/h to 3.45 kg/h. The increase of the inlet air temperature is 10–40 ℃ and the relative humidity is 30%–80%, which reduces the moisture extraction ratio (MER) by approximately 7% and 21%, respectively. The efficiency improvements of the expander and compressor are 0.55–0.8 and 0.4–0.9, respectively, which can deteriorate the energy efficiency of the system by 17% and 36%, respectively. The research results provide new technical references for the application of heat pump technology in the drying field.