Theoretical investigation and comparative analysis of the Linde–Hampson refrigeration system using eco-friendly zeotropic refrigerants based on R744/R1234ze(Z) for freezing process applications

Abstract

The theoretical simulation and thermodynamic analyses of the Linde–Hampson refrigeration system using multiple eco-friendly zeotropic refrigerants are conducted to compare the optimal COP, volumetric refrigerating capacity and irreversibility distribution at the cold space temperature of -45 °C to -25 °C. The genetic algorithm is employed on the global optimization of Linde–Hampson refrigeration system to find out the optimal operating pressures and proportions of mixed refrigerants. By comparison, the most potential binary and ternary refrigerants are selected as R744/R1234ze(Z) and R744/R1234ze(E)/R1234ze(Z), respectively. The temperature glide of ternary refrigerant is mainly regulated by the proportions of the middle-boiling-point and high-boiling-point components. The temperature glide of zeotropic refrigerants should well match the temperature span between heat reservoirs, since the matching degree plays an essential role in system performance, and it can be regarded as an important basis for the selection of mixed refrigerants. The results of comparison with the R744 two-stage compression transcritical refrigeration system and the cascade refrigeration system using R744 and R1234yf show that the Linde–Hampson system using suitable mixed refrigerants can obtain the greatest COP and can be considered as a supplement and alternative. The research results will provide a reference to the applications of the Linde–Hampson refrigeration system using eco-friendly zeotropic refrigerants for freezing process in considerations of environmental protection, safety, and efficiency.