Thermodynamic performance of a modified −150 °C refrigeration system coupled with Linde-Hampson and three-stage auto-cascade using low-GWP refrigerants

Abstract

This study presents a modified vapor compression refrigeration cycle coupled with a Linde-Hampson refrigeration system and a three-stage auto-cascade refrigeration system (LHR-ACR) using low-GWP mixtures as the refrigerant. A mathematical model based on the energy and exergy methods was developed to evaluate the system performances at varied compositions and vapor qualities, including the cooling capacity, coefficient of performance (COP), evaporation temperature, exergy destruction and efficiency. The pinch point analysis for the heat exchangers was also carried out. The results show that the improvement of the system performance is accompanied by the rise of the evaporation temperature and the compressor discharge temperature. Thus, a multi-objective optimization scheme is the most comprehensive and optimum for the design of an LHR-ACR system. Results further indicate that the LHR-ACR system has a better thermodynamic performance with exergy efficiency of 15.18% and COP of 0.1438 at −150 °C when the R1234yf/R32 composition, R170/R14/R50 composition and vapor quality are 0.54/0.46, 0.52/0.22/0.26 and 0.45, respectively. The component that shows the largest exergy destruction is the cascade condenser-III, followed by the ACR air-cooled condenser and ACR compressor, on which future optimization work can be carried out. The proposed new approach and the results obtained in this paper will be valuable for the optimum design and application of the refrigerator at ultra-low temperature levels.