In the post-pandemic era, there is still a high demand for ultra-low temperature storage of vaccine, plasma and biological samples, which can be realized by cascade refrigeration cycles or reverse Brayton cycles. As there is still a research gap on the comprehensive evaluations on reverse Brayton systems using air and cascade refrigeration systems using eco-friendly refrigerants, the thermodynamic and economic analysis models are established for the parallel air cycles and cascade cycles in this study. Based on validated models, the comprehensive performance of the novel reverse Brayton-cascade cycle is studied under different cooling temperatures and cooling capacities. The results show that adding an internal heat exchanger in parallel air cycles could increase the COP and exergy efficiency by 27.12 % and 2.3 %, and save > 31.38 % of total annual cost. However, the comprehensive performance of the composite cycle is inferior to that of cascade refrigeration cycle. The novelty of the paper is to further confirm the superiority of cascade refrigeration systems and the differences between reverse Brayton cycles and cascade cycles, which has not been involved in other studies. This work may supply some technique references for the generation of ultra-low temperature zones and the selection of environmental-friendly refrigerants on CRC establishment.
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