This paper proposes a NH/CO cascade refrigeration system that sets an auxiliary refrigeration loop in the high-temperature cycle to increase the subcooling degree in the low-temperature cycle (CRSS). Based on the basic principles of thermodynamics, a mathematical model is established and theoretical simulation is carried out to obtain the influence of key parameters on the cycle performance. Compared with the conventional cascade refrigeration system (CCRS), the conclusions find that there exists an optimal condensation temperature of low-temperature cycle () to maximize COP. The maximum COP of CRSS is 4.58% higher than that of CCRS when the subcooling degree is 10 °C. The maximum exergy efficiency is 0.391, increasing by 4.40%. With the increase of the subcooling degree, both the COP and the of CRSS increase. When the subcooling degree increases from 5 °C to 15 °C, the performance increment increases from 2.73% to 6.00%. When the evaporation temperature of the system changes, both the COP and exergy efficiency decreases slightly and it is found that the performance is better when the evaporation temperature is lower when condensation temperature is kept constant. Besides, the discharge temperature of the NH compressor in CRSS can be reduced by 9.9 °C when the evaporation temperature is −30 °C.

中文翻译：

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基于NH3制冷剂辅助回路的低温循环过冷NH3/CO2复叠制冷系统能量与火用分析

本文提出了一种在高温循环中设置辅助制冷回路以提高低温循环过冷度的NH/CO复叠制冷系统（CRSS）。基于热力学基本原理，建立数学模型并进行理论模拟，得出关键参数对循环性能的影响。与传统复叠制冷系统（CCRS）相比，结论发现存在一个低温循环的最佳冷凝温度（）以最大化COP。当过冷度为10℃时，CRSS的最大COP比CCRS高4.58%。最大火用效率为0.391，提高了4.40%。随着过冷度的增加，COP和CRSS均增加。当过冷度从5℃增加到15℃时，性能增量从2.73%增加到6.00%。当系统蒸发温度变化时，COP和火用效率均略有下降，发现在冷凝温度保持恒定的情况下，蒸发温度较低时性能较好。此外，当蒸发温度为-30℃时，CRSS中NH压缩机的排气温度可降低9.9℃。