Fig. 6 shows the cycle comparison of R410A and R32 at extreme cooling and heating conditions in a P-h diagram. It can be seen that the enthalpy difference between saturated liquid and vapor lines of R32 is much larger than that of R410A. As the ambient temperature decreases, the pressure difference between the high side and low side also becomes larger. This increases the power consumption, and decreases the system COP. It can also be seen that the condensing and evaporating temperatures of R410A and R32 at the same ambient temperature conditions are quite close.
Fig. 7 summarizes the isentropic and volumetric efficiencies’ comparison for R410A and R32, respectively, in a single stage cycle without vapor injection. The compressor isentropic and volumetric efficiencies are calculated by Equations (9) and (10), respectively. The state points in a P-h diagram are shown in Fig. 8.
It can be seen that the isentropic efficiencies of R410A and R32 are almost the same for all ambient temperature conditions. The volumetric efficiency of R32 was slightly lower than that of R410A. This is mainly due to the fact that the compressor is designed for R410A, and therefore, it cannot reach its optimum performance when the drop-in test is conducted for R32. It was calculated in the property comparison that R32 shows 3% higher in the volumetric capacity, which indicates that the current compressor tested in the system is inappropriately sized for R32.