Performance of Low GWP Refrigerant R-516A in an Air-Cooled Chiller

Many HFC refrigerants have a high global warming potential (GWP), and therefore have the potential to contribute to climate change. Increasing concern due to the presence of greenhouse gases, including high GWP refrigerants, in the atmosphere and their effect on global climate is leading to international policies aimed at phasing down the use of refrigerants with high global warming potentials. The HVAC&R industry is actively developing new environmentally friendly alternatives to replace the high GWP fluids currently in use. R-134a has been widely used in medium pressure refrigerant products, including medium and large capacity chillers, as the replacement for R-12. However, because of R-134a's high GWP(AR5) of 1300, the US EPA, through its Significant New Alternatives Program (SNAP) program, has placed a ban on the use of R-134a in chillers beginning in 2014. R-516A, also known as ARM-42, has been proposed as an alternative to R-134a. R-516A is an azeotropic blend of mostly R-1234yf (77.5%wt) with some R-134a (8.5%wt) and R- 152a (14%wt) that has thermodynamic characteristics very similar to R-134a. R-516A has a significantly lower GWP(AR5) of 130. However, it is mildly flammable, receiving an ASHRAE Standard 34 classification of A2L. Thermodynamic calculations predict that the capacity should be 1.7% lower and the efficiency should be 2.1% lower for R-516A compared to R-134a when operating at conditions typical of the AHRI Standard 550/590 rating point. This paper describes the thermodynamic characteristics of R-516A and reports the results of tests that were performed on a 105 RT (370 kW) air cooled screw chiller with R-134a and R-516A. Performance was measured over a range of ambient air temperatures from 65 degrees F to 125 degrees F (18 degrees C to 52 degrees C). At the AHRI Standard 550/590 rating conditions, measured capacity when running the unit with R-516A was about 2% lower and EER was reduced by 3.5% to 4.0% compared to R-134a. Given these results, R-516A can be considered a design compatible alternative to R-134a in water chiller products.