Performance of R410A and R22 Low GWP Alternative Refrigerants at Elevated Ambient Temperatures

Growing concerns about the global warming impact of refrigerants used in HVAC&R equipment are driving development and evaluation of alternative refrigerants with lower global warming potentials (GWPs). The Air Conditioning, Heating, and Refrigeration Institute (AHRI) recently coordinated the Low-GWP Alternative Refrigerant Evaluation Program (AREP) in which commercial, university, and government laboratories ran tests of a range of alternative refrigerants in a variety of HVAC&R products. This paper reports the performance of a 4.4 RT (15.5 kW) air-cooled water chiller / heat pump run with a number of lower GWP alternative refrigerants. Tests were first run with a compressor designed for R410A-like pressures. The refrigerants tested include R410A (baseline) and R32, along with blends labeled DR-5, DR-4, L-41a, L-41b, ARM70a, ARM-32a, and HPR1D. The compressor was then replaced with one designed for R22-like pressures. The refrigerants tested include R22 (baseline) along with blends labeled DR-4, DR-7, ARM-32a, L-20, LTR4X, and LTR6A. The blends contain R32, R1234yf, R1234ze(E), R134a, R152a, R125, and R744 (CO2). The results of this project have been reported previously for performance measured at the nominal operating condition of 7.2°C (45°F) leaving chiller water temperature and 35°C (95°F) ambient air temperature (Schultz and Kujak, 2012, 2013a, 2013b; Schultz, 2014). In this paper, performance over an extended range of air temperatures from 24°C to 46°C (75°F to 115°F) is reported and compared to a simple thermodynamic cycle model. The predicted performance benefits of some refrigerants were not observed at elevated air temperatures in the equipment tested. However, none of the alternative refrigerants performed significantly worse than R410A at elevated ambient air temperatures.