Experimental research on the heating performance of a single cylinder refrigerant injection rotary compressor heat pump with flash tank

A single cylinder rotary compressor was applied in the refrigerant injection air-source heat pump to improve the heating performance in cold regions. In this study, the performance of an R410 A single cylinder rotary compressor vapor injection（SCRCVI） system was measured and analyzed by varying the compressor frequency f and injection pressure Pi njat the ambient temperature To d=–10°C.The experimental results indicated that an optimum injection pressure to gain the maximum COPh （coefficient of performance） existed in the SCRCVI cycle. However, the maximum COPh of the SCRCVI system decreased as the increase of the frequency, and the maximum COPhwas even lower than that of the CSVC system at high compressor frequency. Therefore, in view of the energy saving and emission reduction, the SCRCVI system should be switched to single stage compression system when the heating capacity demand could be satisfied at high compressor frequency f. Compared to the conventional single-stage vapor compression（CSVC） system, refrigerant injection could enhance the heating capacities and COPh by 28.2% and 7.91%, respectively. The average total mass flow rate of the SCRCVI system was 24.68% higher than that of the CSVC system. As the SCRCVI system worked at the optimum injection pressure, the variation trends of the different system parameters were investigated in detail. These trends were reliably used to optimize the refrigerant injection system design and the control strategy. The parameter of(Pinj–Ps) could be adopted as the signals to control the opening of the upper stage electronic expansion valve EEV1.