An experimental study was conducted in which the performance of three blends of R134a and R32 was compared to that of R22. The effect of refrigerant charge on the performance of these refrigerants in an air-to-air heat pump operating in the cooling mode was quantified. The mixtures consisted of 40%/60%, 30%/70%, and 20%/80% ratios (by mass) of R32 and R134a. Charge levels of 5.00, 5.45, 5.90, and 6.00 kg (11, 12, 13, and 14 lb) were tested. At each charge level, outdoor room conditions of 27.8 deg C, 35.0 deg C, and 40.6 deg C (82 deg F, 95 deg F, and 105 deg F) were tested. The expansion device for all tests was a 1.96mm (0.077 in.) diameter orifice. Three variables were used to quantify refrigerant performance - total capacity, total electrical power consumption, and coefficient of performance (COP). The performance of the heat pump with any of the three mixtures was not as good as with R22. The capacities were between 7% and 17% less than with R22. The best COPs with the mixtures were within 3% of that with R22 in some cases, but the corresponding capacities at these COPs were approximately 12% lower than that in the R22 base case. The best results for a mixture were with the 40%/60% blend. The capacity was 7.3% less than the base case and the COP was 8.5% lower.

KEYWORDS: cooling, performance, air air heat pumps, R22, R32, R134a, refrigerants, mixtures, experiment, comparing, testing, coefficient of performance, electricity consumption, energy consumption, capacity