R448A和R455A在复叠制冷系统中替代R404A的性能分析

现阶段广泛使用的R404A制冷剂的GWP值（全球变暖潜能值）较高、对环境不友好，为了探究GWP值较低的新型替代制冷剂对制冷系统性能的影响，本文建立了复叠制冷系统的热力学模型，研究了R455A和R448A制冷剂在不同工况下的性能表现，并从低温级蒸发温度、高温级冷凝温度、中间温度，以及高、低温级过冷度等方面与R404A系统进行对比分析。结果表明，在不同工况下，R455A/R23系统的COP（制冷系数）始终最高，R404A/R23系统的COP最小。在相同蒸发温度下，R455A/R23和R448A/R23系统的最佳中间温度低于R404A/R23系统，最佳COP分别比R404A/R23系统高6.77%，5.25%。另外，高温级过冷度增加会使系统COP增大，其中，R404A/R23系统COP的增加幅度最大，R448A/R23系统COP的增加幅度最小，而低温级过冷度的增加则会使系统性能下降。

Performance analysis of R448A and R455A replacing R404A under cascade refrigeration system

Due to the high GWP value (global warming potential) of R404A refrigerant which is widely used at present and unfriendly to the environment, it has been increasingly urgent to find a suitable low GWP refrigerant. In order to explore the effect of new alternative refrigerant with low GWP value on the performance of refrigeration system, the thermodynamic model of cascade refrigeration system was established, and the performance of the new alternative refrigerants R455A and R448A with low GWP value under different working conditions was studied. These results were compared with the R404A system in terms of evaporation temperature of low temperature stage, condensation temperature of high temperature stage, interstage temperature and subcooling degree of high and low temperature stages. The results indicate that the COP (coefficient of performance) of R455A/R23 system is always the highest and the COP of R404A/R23 system is the lowest under different working conditions. Under the same evaporation temperature, the optimum interstage temperature of R455A/R23 and R448A/R23 system is lower than that of R404A/R23 system. The optimum COP of R455A/R23 and R448A/R23 system is 6.77% and 5.25% higher than that of R404A/R23 system. In addition, the increase of high temperature level undercooling will increase the COP of cascade system. The increase of COP in R404A/R23 system is the largest, and the increase of COP in R448A/R23 system is the smallest.The increase of low temperature level undercooling will degrade the system performance.