Abstract: In light of the low-temperature cycle in the cascade refrigeration system using blends of CO2/R170, the mathematical models of solid-liquid equilibrium and vapor-liquid equilibrium were developed.The models were used to determine the range of mixing ratio in which crystallization of the mixture at a low temperature could be prevented.The cycle performance and flammability of mixed refrigerants with different mixing ratios were analyzed.The impact of mixing ratio on cycle performance and flammability was investigated.The effects of medium temperature on the whole COP of the cascade refrigeration system using R290 as high-temperature circuit refrigerant and blends of CO2/R170 as low-temperature circuit refrigerant were analyzed.A better refrigerant for the low-temperature circuit of cascade refrigeration system was found.

摘要： 针对CO2/R170混合物在复叠式制冷系统低温环路使用的工况，建立了固液平衡和汽液平衡的数学模型，决定了保证混合物在较低温度下不结晶的配比。在一定的配比范围内对混合物进行了循环性能和可燃性分析。研究了混合物配比对循环性能参数和可燃性的影响，以及中间温度在高温环路使用R290、低温环路使用CO2/R170混合物时，复叠式制冷系统整体制冷系数（COP）的变化趋势。研究表明，这种混合物适宜作为复叠式制冷系统低温环路的制冷剂。