Fig. 12 shows the injection pressure comparison between R32 and R410A. Typically the injection pressure increases with increasing ratio. The injection pressure is directly affected by the upper-stage expansion valve. As the upper-stage expansion valve opening increases, the injection pressure increases. Therefore, more vapor refrigerant is injected to the compressor, and increases the injection ratio. Fig. 13 shows the compressor discharge temperature comparison between R32 and R410A.
 Fig. 13 also shows that the discharge temperature of R32 is higher than that of R410A. The reason is the volumetric efficiency of R32 is lower than that of R410A, which resulted in lower refrigerant mass flow rate and higher discharge temperature. This observation is further explained later. For both the heating and cooling modes, the compressor discharge temperature decreases with the increasing injection ratios. Increasing injection ratio means that more refrigerant is injected to the compressor to provide better compressor cooling, and therefore decreases the compressor discharge temperature. To better understand the vapor injection benefits for R32 and R410A, the system performance with the same injection ratio was compared. The injection ratio was selected from the experimental results that show closest match of the injection ratios of R32 and R410A. In such case the R410A performance with vapor injection was used as the baseline.