Abstract: Vapour-Injected Heat pump (VIHP) can improve the efficiency and reliability of the heat pump system, and the heat pump system using R290 as the working fluid has a good prospect. In this paper, a thermodynamic model of VIHP with a subcooler using R290 is established and the influence of the evaporation temperature, condensation temperature, relative intermediate pressure and relative vapour injection mass flow on the performance of the system is analyzed. The results show that under the maximum allowable relative vapour injection mass flow, reducing the condensation temperature and increasing the evaporation temperature during cooling will reduce the cooling capacity, while reducing the evaporation temperature during heating is conducive to the improvement of COP. The relative intermediate pressure has a significant effect on the maximum allowable relative vapour injection mass flow.In addition, an increase in relative intermediate pressure will reduce heating capacity and power consumption, but will increase COP. The system performance parameters under the maximum relative vapour injection mass flow are studied, which provides a reference for greatly reducing the system exhaust temperature and improving system performance.

Key words: Vapour injection, Maximum relative vapour injection mass flow rate, Intermediate pressure, R290