The thermodynamic and environmental analysis of a variable speed R404A refrigeration system using R455A

•R455A has a higher COP about by 4.3% compared to R404A.•Exergy efficiency of R455A is better than R404A.•The influence of compressor speed on COP, exergy efficiency and TEWI is determined.•CO2 emissions are diminished using R455A as a substitute for R404A in the system.•An empirical expression for COP versus compression ratio is proposed. The suitability of drop-in application of low-GWP refrigerant R455A in a R404A refrigeration system is experimentally investigated in this paper comparing energy performance and environmental impacts (i.e., CO2 emissions) of the system. The evaporation temperatures are −5, 0 and + 5 °C while condensation temperatures are 30, 40 and 50 °C in the test conditions. Besides, the compressor speed is adjusted for three cases as 40, 45 and 50 Hz. The behaviours of COP, exergy efficiency and total equivalent warming impact (TEWI) are determined depending on evaporation and condensation temperatures as well as compressor speed. The results demonstrate that although cooling capacity of R404A is higher, COP of R455A is computed to be better than R404A about by 4.3 % (on average) for all covered cases. The exergy efficiency of R455A is also found to be higher compared to R404A. The COP and exergy efficiency values are reduced, TEWI enhances as compressor speed increases for both R404A and R455A. Additionally, an empirical expression (valid within about ± 5 % and independent of variable parameters such as refrigerant type, compressor speed as well as evaporation and condensation temperatures) is proposed for the relationship between nondimensional parameters COP and compression ratio. Furthermore, the amount of TEWI is verified to be lower for R455A than R404A, hence the studied alternative blend can be preferred due to the environmentally friendly characteristic. It can be suggested referring to the obtained results that R455A can be directly used in a R404A refrigeration system due to improved thermodynamic performance and diminished CO2 emissions.