Effect of refrigerant charge variation of R32 as drop-in replacement for R22 in air conditioning system

Relatively, R32 has very low GWP compared to R22, and therefore leading R32 to be a potential substitute for R22. This paper investigates the performance changes due to drop-in replacement of R22 to R32 in a residential air conditioner. The liquid density ratio between R32 and R22 at 0°C is 0.82. As a result, theoretically, for drop-in 100% from R22 with R32, the refrigerant charge amount of R32 is 82% of R22 (by mass). In this experiment, the refrigerant charge mass of R32 is varied from 90% to 105% with 5% increment for each measurement. Experimental results show that the optimal refrigerant charge amount is 95%. At this optimal refrigerant charge amount, the mass ratio of R32 to R22 is 77.9%. Meanwhile, at this mass ratio, the cooling capacity increased by 7.7% and COP decreased by 12.1%.