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

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