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摘 要： NH3/CO2组合制冷系统是完全自然工质制冷系统。在分析NH3/CO2复叠制冷循环系统和NH3/CO2相变二次冷媒系统的T－S图和P－H图的基础上，分别比较了这两种系统在一定工况下的COP、NH3用量和CO2用量。计算结果表明这两个系统的COP都存在极值，但是NH3/CO2复叠制冷循环系统的COP受运行工况影响更加明显；对于CO2用量而言，NH3/CO2复叠制冷循环系统CO2用量要大于NH3/CO2相变二次冷媒系统CO2用量；对于NH3用量，这两种系统用量没有明显差别。这说明NH3/CO2相变二次冷媒系统在低温系统运行更加安全和可靠。 关键词 ：制冷 相变二次冷媒 复叠制冷 自然工质 Performance Comparison Of Two Different Combined Refrigeration Systems Of Nh3/Co2 Liu Bin Cai Jinhui Dong Xiaoyong Zang Runqing Tianjin Key Lab of Refrigeration Technologies, Tianjin University of Commerce, 300134 Abstract The combined refrigeration system of NH3/CO2 is the completely friendly refrigeration system using nature refrigerants. Based on the analyses of T-S and P-H diagram of the NH3/CO2 cascade refrigeration system and the NH3/CO2 phase change secondary medium refrigeration system, COP, the quantity of NH3 and CO2 of the two systems were compared. The calculated results show that COP have a maximum value about the two system, but the maximum value of COP of the NH3/CO2 cascade refrigeration system is more easily affected by the working conditions that that of the NH3/CO2 phase change secondary medium refrigeration system. As for the quantity of CO2, the value of the NH3/CO2 cascade refrigeration system is larger than that of the NH3/CO2 phase change secondary medium refrigeration system. But as for the quantity of NH3, there is little difference between the two systems. This implies that under low temperature, the NH3/CO2 phase change secondary medium refrigeration system is safer. Keywords Cefrigeration Phase change secondary medium Cascade refrigeration Nature refrigerant