alternative refrigerants, elevated ambient temperature, water chiller, air-cooled
Growing concerns about the impact on the environment of the 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 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 will report the performance of an ~4.4 RT 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, ARM-70a, 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) in various compositions. 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) air temperature (Schultz and Kujak, 2012, 2013a, 2013b; Schultz, 2014). In this paper, performance over an extended range of air temperatures from 25°C to 45°C (77°F to 113°F) will be reported and compared to a simple thermodynamic cycle model. As already reported, the predictions of the thermodynamic cycle model and measured performance are in good agreement at the nominal operating condition. However, some deviations were observed between the measured and modeled performance for air temperatures away from the nominal condition. In particular, the predicted performance benefits of some refrigerants were not observed at elevated air temperatures. On the other hand, none of the alternative refrigerants performed significantly worse than R410A at elevated air temperatures. These discrepancies indicate there are factors that need to be accounted for other than the thermodynamic properties of the refrigerants. These factors will be discussed here. Schultz and Kujak, 2012, “TEST REPORT #1?–?System Drop-in Test of R-410A Alternative Fluids (ARM-32a, ARM-70a, DR-5, HPR1D, L-41a, L-41b, and R-32) in a 5-RT Air-Cooled Water Chiller (Cooling Mode)”, AHRI Low-GWP Alternative Refrigerants Evaluation Program website, http://www.ahrinet.org/ahri+low_gwp+alternative+refrigerants+evaluation+program.aspx Schultz and Kujak, 2013a, “TEST REPORT #6?–?System Drop-in Tests of R-22 Alternative Fluids (ARM-32a, DR-7, L-20, LTR4X, LTR6A, and D52Y) in a 5-RT Air-Cooled Water Chiller (Cooling Mode)”, AHRI Low-GWP Alternative Refrigerants Evaluation Program website, http://www.ahrinet.org/ahri+low_gwp+alternative+refrigerants+evaluation+program.aspx Schultz and Kujak, 2013b, “Comparative performance of low GWP alternate refrigerants for R410A and R22 in a small air-cooled chiller”, Proceedings of ICCR3013 – 5th International Conference on Cryogenics and Refrigeration, 06-09 Apr 2013, Hangzhou, China, Paper ID B-4-09. Schultz, 2014, “Performance of R410A and R22 Alternative Lower GWP Refrigerants in a Small (~5 RT) Water Chiller”, presented at the ASHRAE Winter Conference, 19-22 Jan 2014, New York City, Conference Paper NY-14-C066.