Abstract: The auto-cascade refrigeration cycle is characterized by its simple design, stable operational characteristics, broad cooling temperature range, and promising applications, making it a focal point in the field of low-temperature research. However, the traditional auto-cascade refrigeration cycle (BACR) is limited by refrigerant flow rate within the evaporator, typically addressed by reducing evaporation pressure to enhance cooling capacity. This approach leads to the issues such as high compressor power consumption, high exhaust temperature and low refrigeration efficiency. Researchers have extensively explored refrigerant component ratio optimization and system process improvements to address these issues. However, previous cycles are relatively complex, posing challenges to stable operation for the systems. Thus, a simple and effective cycle improvement scheme is necessary for practical applications. This work proposes a novel throttling-enhanced auto-cascade refrigeration cycle (VACR). This configuration reduces the pressure of the two-phase refrigerant mixture at the condenser outlet through a throttling process, promoting partial evaporation of the liquid phase and increasing the refrigerant flow rate into the evaporator. Using R1150/R600a as the refrigeration, a thermodynamic model of the cycle is established, and the effects of key parameters such as component ratio, condenser outlet vapor quality, condensation temperature, and evaporation temperature on thermodynamic performance are analyzed. The results show that when the R1150 component ratio ranges from 0.45 to 0.60, the VACR increases the refrigerant flow rate within the evaporator by 15.1% to 17.0% compared to the BACR. The highest coefficient of performance (COP) of the VACR is 0.743, representing a 14.54% improvement over the BACR. When the condensation temperature ranges from 30℃ to 40℃, the COP of the VACR increases by 13.82% to 31.19% compared to the BACR. When the evaporation temperature ranges from -60℃ to -70℃, the cooling capacity of the VACR increases by 19.43% to 56.11% compared to the BACR. Overall, the comparative analysis highlights the thermodynamic performance improvement potential in the proposed VACR.

Key words: zeotropic mixture, auto-cascade refrigeration cycle, coefficient of performance, thermodynamic analysis

摘要： 自复叠制冷循环凭借结构设计简单、运行特性稳定、制冷温区宽以及广阔的应用前景，已成为目前低温领域的研究热点。传统自复叠制冷(BACR)循环由于进入蒸发器的制冷剂工质流量较小，通常采用降低蒸发压力的方式来提高制冷量，这会引起压缩机耗功高、排气温度高及制冷效率低等问题。为此，研究者们从工质组分优化、系统流程改进等方面开展了广泛的研究，但以往提出的循环结构较为复杂，给系统稳定运行带来挑战。因此，一种简单有效的循环改进方案更具实际应用价值。本工作创新性地提出节流增效自复叠制冷(VACR)循环，通过节流过程降低冷凝器出口气液两相混合工质的压力，促使部分液相工质蒸发，从而增加蒸发器进口工质流量。本工作以R1150/R600a为工质，建立循环热力学数学模型，对比分析了组分配比、冷凝器出口干度、冷凝温度和蒸发温度等关键参数对循环性能的影响。结果表明，当R1150的组分配比为0.45~0.60时，VACR循环通过节流效应，使进入蒸发器的制冷剂流量较BACR循环增加15.1%~17.0%；VACR循环COP最高达0.743，相比于BACR循环提升14.54%；在冷凝温度为30~40℃时，VACR循环的COP相比于BACR循环提升13.82%~31.19%；当蒸发温度为-60~-70℃时，VACR循环的制冷量较BACR循环提升19.43%~56.11%。综上，对比分析突出了VACR循环在热力学性能方面的改进潜力。

关键词: 非共沸混合工质, 自复叠制冷循环, 性能系数, 热力学分析