6. Conclusions
This paper investigates the performance difference between R410A and R32 in a vapor-injected heat pump system with a flash tank. Drop-in test was performed with R32 in the heat pump system for both cooling and heating conditions. A single-stage cycle without vapor injection and a two-stage cycle with vapor injection have been tested. Through experimentation, it was found that the capacity improvement of R32 over R410A was between 3% and 10%, and the COP improvement was between 2% and 9% for the single-stage cycle without vapor injection. For the two-stage cycle with vapor injection, different injection ratios were investigated for R410A and R32. The benefit of vapor injection was significant. The maximum capacity improvement for R410A and R32 was observed to be 33% and 25%, respectively. The maximum COP improvement for R410A and R32 was observed to be 18% and 11%, respectively. The improvement was most pronounced at the heating condition of "18 #C. The system performance using R32 and R410A was also directly compared in vapor injection mode. Comparing R32 to R410A at the same injection ratio and using R410A as the baseline, the capacity improvement was found to be 2e7%, and COP improvement was found to be 1e6%. There was no improvement at extreme cooling and heating conditions. The inferior performance of R32 at the extreme conditions is mainly due to the refrigerant mass flow rate decrease caused by the compressor efficiency degradation. High compressor discharge temperature also reduces the reliability of system operation due to the possibility of lubricating oil performance degradation.