新型CO2超音速两相膨胀制冷循环的理论研究

本文提出了以Laval喷管为核心部件的超音速两相膨胀机的概念，构建了以天然制冷剂CO2为工质的超音速两相膨胀制冷循环模型并对其进行理想循环热力学分析和模拟计算研究。结果表明：超音速两相膨胀机入口压力、入口温度和旋流分离段出口压力均对系统制冷性能有影响；在空调温区工况，CO2超音速两相膨胀制冷循环COP为6.69，是现有制冷性能相对最优的CO2跨临界制冷循环COP的1.63倍，且大幅降低系统压力；气液分离时液相速度损失对系统制冷性能有影响，系统COP由9.56减至6.01，相对卡诺效率由0.95减至0.60，但仍然保持在较高水平。通过初步的热力学分析和模拟计算研究表明，新型CO2超音速两相膨胀制冷循环具有较好的原理可行性和发展前景。

Theoretical Study of a Novel CO2 Supersonic Two-phase Expansion Refrigeration Cycle

Natural refrigerants such as CO2 have become a research hotspot. Under high-pressure conditions, a large throttling loss becomes the primary reason for the low circulation efficiency of the CO2 refrigeration cycle. Therefore, reducing the throttling loss is an effective method to improve efficiency. This study proposes a supersonic two-phase expander with a Laval nozzle as the core component. A CO2 supersonic two-phase expansion refrigeration cycle model is established, and an ideal cycle thermodynamic analysis and simulation investigation are conducted. The results show that the inlet pressure and temperature of the supersonic two-phase expander and the outlet pressure of the cyclone separation section affect the cooling performance of the system. The coefficient of performance (COP) of the CO2 supersonic two-phase expansion refrigeration cycle is 6.69, which is 1.63 times that of the existing CO2 transcritical refrigeration cycle, with relatively optimal refrigeration performance. Additionally, the operating pressure of the system is considerably reduced. The loss of liquid-phase velocity during gas-liquid separation affects the refrigeration performance of the system. The COP of the system decreases from 9.56 to 6.01, and the relative Carnot efficiency decreases from 0.95 to 0.60; however, it still remains at a high level. The preliminary thermodynamic analysis and simulation show that the proposed CO2 supersonic two-phase expansion refrigeration cycle is feasible and exhibits good development prospects.