Figure 15 summarizes the comparison of low-stage and high stage isentropic and volumetric efficiencies for R410A and R32 in a two-stage cycle with vapor injection. The low-stage and high-stage compressor efficiencies are calculated using Equations (11)-(14). The state points in a P-h diagram are shown in Fig. 16. It can be seen that at the ambient temperature of 46 #C and "18 #C, the isentropic efficiencies remain almost the same, yet the volumetric efficiencies of R32 were significantly lower than those of R410A. This explains the significant refrigerant mass flow rate decrease in these conditions, as seen in Fig. 14b. The volumetric and isentropic efficiencies remain almost the same for other temperature conditions.