| 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.This paper is focused on the performance of ACR system using in 230K temperature range. Some useful results, such as suitable refrigerants, their mixing prpportion and the corresponding working condition are gained through experimental and theoretical study.Based on the thermodynamic analysis and Equation of State (EOS) of RKS, the material properties can be calculated by programming. Then the theoretical model of ACR system is established, and the simulation results are gotten. With different mixing proportion, the different performances of refrigerator under some and different working conditions are simulated. The following results are provided: suitable refrigerants, their mixing proportion and the measures that should be taken when the working conditions changed.An experimental apparatus has been set up and experiments have been carried out successfully. The refrigerator was designed on the basis of simulating results. The refrigerant is composed of R744, R290 and R600a. A one-stage compressor used in air-conditioning is applied and the refrigerating temperature can reach below 230K. In term of experiment safety, the R502 is applied instead of R290 in the preliminary experiment. Under different operating conditions, the performance of refrigerator with different proportion is investigated. According to a series of experimental data, the impacts of following factors on the stability and refrigerating performance are analyzed: mixing proportion, charging quantity, calefaction and throttle valve. The results of this paper are of great importance for further research.
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