Energy and exergy performance evaluation of a three-stage auto-cascade refrigeration system using low-GWP alternative refrigerants

Abstract

l Performance of mixtures consisting R1234yf, R170, R41 and R1132a were investigated within a three-stage ACR. l All alternatives presented promising energy results and can be recommended to replace R23. l The isobaric 3D and the isothermal-isobaric ternary VLE diagrams were presented. l R1234yf/R23/R14 (0.59/0.24/0.17) offers the maximum COP and exergy efficiency of 0.614 and 26.15%. l R1234yf/R41/R14 (0.64/0.17/0.19) is suggested as a promising alternative refrigerant at -100 °C. In order to seek promising refrigerants for vapor compression refrigeration system to obtain ultra-low temperatures down to -100 °C, and to determine whether the low-GWP refrigerants, R41, R170 and R1132a, are suitable substitutes for R23, this study conducted a comprehensive comparative analysis on the cycle characteristics of a three-stage auto-cascade refrigeration (ACR) system using R1234yf/R23/R14, R1234yf/R41/R14, R1234yf/R170/R14 and R1234yf/R1132a/R14. The system performances, including cooling capacity, coefficient of performance (COP), evaporation temperature, compressor discharge temperature, exergy destruction and efficiency were investigated with various compositions and vapor qualities. Results show that R41, R170 and R1132a can all be recommended to replace R23, and the alternatives present promising thermodynamic properties in theoretical simulations. Under the same operation conditions, the cooling capacity of the R1234yf/R41/R14 system is the largest, while the maximum COP and exergy efficiency occur in the R1234yf/R23/R14 system. Considering the energy shortage and environmental pollution issues, R1234yf/R41/R14 with the mass fraction of 0.64/0.17/0.19, COP of 0.2713, and exergy efficiency of 13.91% performs better and hence can be suggested as an alternative refrigerant for the three-stage ACR operating at -100 °C. The largest exergy destruction component occurs in the compressor, followed by the air-cooled condenser and expansion valve, on which future optimization work can be carried out. The results provide a basic theoretical analysis of the selection and replacement of refrigerant in three-stage ACR.