Experimental evaluation of the azeotropic mixture R516a as an R134a drop-in alternative for moderately high-temperature heat pumps

The moderately high-temperature heat pump (MHTHP) is a market with a great potential to reduce greenhouse gas emissions from the heating sector. However, future proof MHTHPs cannot be based on hydrofluorocarbons with high global warming potential (GWP). Fourth-generation refrigerants with GWP below 150 are required. This work experimentally investigates the new azeotropic mixture R516A as a drop-in alternative to R134a, with a low GWP (142). Measurements are taken from a test rig at different steady-state operating conditions. The evaporating temperature is 7.5 ºC, 15 ºC and 22.5 ºC, and condensing temperature varies between 55 ºC and 75 ºC, at steps of 5 ºC. R516A presents a lower discharge temperature (average reduction of 7 ºC), which provides a safer operation for the compressor and increases its lifespan. R516A heating capacity reduction is 13.5% on average, with a reduced heating effect and comparable compressor power consumption. R516A shows a 12% COP reduction at higher evaporating temperatures.