Experimental research on vapor-injected heat pump using injection subcooling

A newly designed vapor-injected heat pump using injection subcooling was adopted to improve the heating performance of an R32 heat pump at cold regions. A composite test system was used to research the system working performance. Four kinds of system: single stage system (SS system), vapor injection system (VI system), vapor injection with subcooling system (VIS system) and liquid injection system (LI system) were tested and heating performance was compared with each other. The results showed that, vapor injection with subcooling can further decrease the R32 compression discharge temperature and made the system run under evaporating temperature lower to −20 °C; Heating performance was affected by the ratio of subcooling medium flow rate, and there is an optimum value for each evaporating temperature; Compared with LI system, the Coefficient of Performance (COP) of VIS system can be enhanced by 11.2%-13.6%.