Experimental study on the thermal performance of R600a, R290 and R600a/R290 mixtures in a retrofit R134a refrigeration system

Refrigeration systems play paramount roles in life quality of human beings and social development in terms of food security, environmental impact, and energy efficiency. The traditional CFC, HCFC, and HFC refrigerants have been in the process of phase-out and being replaced by the sustainable working fluids. In this paper, the experimental thermodynamic performance evaluation of the hydrocarbons R600a, R290 and their mixtures used in a vapour compression refrigeration system that utilizes R134a as a working fluid was carried out. Firstly, a theoretical analysis was developed to evaluate the feasibility of the retrofit by employing the vapour compression refrigeration cycle. The evaporation temperatures were ranging from -25 °C to 3 °C, and the condensation temperatures ranging from 25 °C to 65 °C with superheating and subcooling degrees constant at 5 °C. The thermodynamic and thermophysical properties were obtained using REFPROP software. Lastly, based on the results obtained from the theoretical analysis, the experimental comparison of the refrigeration cycle performance was conducted using a refrigeration system designed for R134a. The results show that both pure R600a and R290 cannot be recommended as drop-in substitutes for R134a due to their significant differences in thermophysical properties. A mixture of R600a/R290 50%/50% composition was found to be the most appropriate alternative refrigerant for the R134a system retrofit with a comparative thermal performance.