| Cascade refrigerating systems are widely used in quick freezing, preservation of biological tissues, cooling detectors. The Auto Cascade Refrigeration Cycle (ACR) requires only one compressor with the non-azeotropic refrigerant mixture (NARM), which is very popular for its particular excellence.The aim of this paper is to study the performance of ACR system used in -40℃ temperature range, and get some useful results, such as suitable refrigerants, their mixing proportion and the working performance through theoretical computation and experimental study.Based on the thermodynamic analysis and equation of state (EOS) of RKS, the material properties were calculated by programming. Then the theoretical model of ACR system is established, and the simulation results are got. Through theoretical analysis, the selection principle of mixed refrigerants is studied, and some useful results are got. The system's performances of mixed refrigerants of different proportion at different working conditions are gainedA series of experiments are carried out using mixed refrigerants of R744/R290 and R744/R290/R600a of different proportion. A one-stage compressor used in air-conditioning is applied in this refrigerator. The refrigerating temperature can reach below 230K, the refrigerator can run steadily and the performance is very good. Through experimental study, the theoretical results are validated, and some new conclusions are got.
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