This study aimed to optimize the heat production performance of an enhanced vapor injection air source heat pump system with R32. Combined with the structure and actual operation characteristics of a scroll compressor system

a complete mathematical model was established and programmed using MATLAB. After verification of the simulation results with experimental data

the influences of the vapor injection pressure of the system

and the specific volume ratio of the quasi-one-stage compression on the relative vapor injection volume of the system were explored under different ambient temperatures. It was found that the vapor injection heat pump system is more suitable for operation at ambient temperatures of below ?10 °C than an ordinary heat pump system. The optimal operating range of the heating mode of the air-source heat pump system with vapor injection was obtained. Because the specific volume ratio of the quasi-one-stage compression of the system is 1.1

the relative vapor injection volume is the maximum. When the ambient temperature is below -10 °C

within ?10– -5 °C or above -5 °C respectively

the optimal relative injection volume should be within 0.22–0.33

0.20–0.22 and 0.18–0.20 respectively. The corresponding optimal relative inject pressure ranges 0.85–1.31. Within the range of the optimal vapor injection parameters

the advantages of the enhanced vapor injection air-source heat pump system with R32 are obvious.