Thermodynamic performance of R502 alternative refrigerant mixtures for low temperature and transport applications

In this study, two pure hydrocarbon refrigerants, R1270 (propylene) and R290 (propane), and three binary mixtures composed of R1270, R290 and R152a were tested in a refrigerating bench tester with a scroll compressor in an attempt to substitute R502, which is used in most low temperature and transport refrigeration applications. The test bench provided 3–3.5 kW capacity, and water and water/glycol mixture were employed as the secondary heat transfer fluids. All tests were conducted under the same external conditions, resulting in the average saturation temperatures of −28 and 45 °C in the evaporator and condenser, respectively. The test results showed that all refrigerants tested had 9.6–18.7% higher capacity and 17.1–27.3% higher COP than R502. The compressor discharge temperature of R1270 was similar to that of R502, while those of all the other refrigerants were 23.7–27.9 °C lower than that of R502. For all alternative refrigerants, the charge was reduced up to 60% as compared to R502. There, of course, was no problem with mineral oil, since the mixtures were mainly composed of hydrocarbons. Since some of them are mixtures, one can change their compositions a little to suit various needs in many applications without significant deterioration of the performance. Overall, these alternative refrigerants offer better system performance and reliability than R502 and can be used as long term substitutes for R502 due to their excellent environmental properties.