Mechanical subcooling is an efficient means of enhancing the performance of CO2 transcritical refrigeration systems. With the aim of further improving the system performance, this objective of this paper is the comparative analysis on mechanical subcooling CO2 transcritical refrigeration system integrated with throttling valve (MCVS) and expander (MCES). A thermodynamic model for parametric analysis was developed on energy, exergy and economic perspectives. The model is validated with literature data. The simulation results indicate that there exists simultaneously optimum discharge pressure and subcooling degree maximizes the COP of MCVS and MCES. While the cooling capacity of MCES is 4.30 %–5.67 % lower than that of MCVS at a given CO2 mass flow rate, the incorporation of expansion work recovery leads to a total power consumption reduction of 8.53 %–11.29 % for MCES compared to MCVS, resulting in a corresponding increase in COP by 10.01 %–11.11 %. Additionally, exergy efficiency is improved by 10.74 %–11.48 %. Despite the addition of an expander in the MCES system, it offers advantages such as a smaller scale and lower power consumption for the mechanical subcooling system, ultimately leading to superior economic benefits compared with the MCVS system.

中文翻译：

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带膨胀阀和节流阀的机械过冷跨临界 CO2 制冷系统的热力学分析和比较


机械过冷是提高 CO2 跨临界制冷系统性能的有效方法。为了进一步提高系统性能，本文的目标是对集成节流阀 （MCVS） 和膨胀器 （MCES） 的机械过冷 CO2 跨临界制冷系统进行比较分析。从能源、用能和经济角度开发了用于参数分析的热力学模型。该模型使用文献数据进行了验证。仿真结果表明，同时存在最佳排放压力和过冷度，使 MCVS 和 MCES 的 COP 最大化。虽然在给定的 CO2 质量流量下，MCES 的冷却能力比 MCVS 低 4.30 %–5.67 %，但与 MCVS 相比，结合膨胀功回收导致 MCES 的总功耗降低了 8.53 %–11.29 %，从而导致 COP 相应地增加了 10.01 %–11.11 %。此外，用能效率提高了 10.74 %–11.48 %。尽管 MCES 系统中增加了膨胀器，但它为机械过冷系统提供了规模更小、功耗更低的等优势，最终与 MCVS 系统相比，具有卓越的经济效益。