Experimental performance of a combined throttling device with stepper motor and needle valve in an ammonia-water absorption refrigeration system

Electronic expansion valves (EEVs) for ammonia-water absorption refrigeration systems are expensive and limited in model selection. In this paper, a combined throttling device (CTD) based on a stepper motor and needle valve is proposed to replace the electronic expansion valve (EEV). An experimental platform was established to study its performance. Results show that with PID, fuzzy, and fuzzy PID superheat degree control algorithms, the maximum deviation of the superheat degree is no more than 1°C, and fuzzy PID reduces fluctuation by 14.6% at the superheat degree of 9.5°C compared with PID. At the superheat degree of 9.5°C, the system performs refrigerating capacity of 2.8kW and COP of 0.48. The experimental results validate the practical feasibility and engineering application potential of the proposed CTD for ammonia-water absorption refrigeration systems.