| 摘要: |
| 随着国际社会环境意识的提高，臭氧层破坏、温室效应问题受到持续广泛的关注，越来越多的学者将注意力集中于环保制冷剂。CO2由于简单易得、安全可靠、传热性能和流动性好等优点受到重视。本文对CO2气液两相小型膨胀机的研究进展进行分析和总结，发现：在循环中将节流阀换成CO2膨胀机可以有效提高系统的制冷效率，经过计算得到带膨胀机跨临界CO2循环的制冷、制热效率分别比R134a循环高6.9%、4.6%，比带节流阀的循环高25.76%、16.17%；CO2膨胀机的等熵效率越高，系统制冷、制热效率越大，若CO2膨胀机的等熵效率大于32%，则带CO2膨胀机的系统性能优于带回热器循环的系统性能。不同CO2膨胀机由于结构不同导致效率、泄漏和摩擦损失不同，活塞式、转子式等膨胀机结构简单，但同时泄漏损失也较大；滑片式、旋转叶片式、涡旋式等膨胀机效率得到了很大的提高，但其结构较为复杂，制造较为麻烦，生产成本较高；同时对当前存在的一些问题提出了解决办法，如进行合理的设计减小泄漏与摩擦损失、将压缩功提供给压缩机、在膨胀过程中加入其他气体以及设计可调节膨胀比的CO2膨胀机。目前CO2膨胀机的研究基本都集中于实验室，在工程中应用较少。因此未来应以实验和理论相结合，进一步研究CO2膨胀机效率提升、关键零部件技术开发等问题。 |
| 关键词: 跨临界循环 膨胀机 膨胀功 等熵效率 泄漏 CO2 |
| DOI： |
| Received:March 24, 2022Revised:May 03, 2022 |
| 基金项目:国家重点研发计划课题（2021YFF0306801，2021YFF0306805）和中国制冷学会课题项目（CAR20190701）资助。 |
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| Research Progress of Small-scale CO2 Two-phase Expanders |
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Qin Pengwei1, Ma Yitai1, Dang Chaobin2, Liu Kai3, Li Minxia1, Huo Wenming1, Wang Pai1
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| (1.Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, MOE, Thermal Energy Research Institute, School of Mechanical Engineering, Tianjin University;2.School of Engineering, University of Fukui;3.EUROJOY Ice & Snow Investment Management (Beijing) Co. Ltd.) |
| Abstract: |
| With the increased awareness in the international community, the problems of ozone depletion and greenhouse effect have received extensive attention, more and more scholars are focusing on environmental-friendly refrigerants. CO2 demonstrated its value in terms of simplicity, availability, safety, reliability, and good heat transfer performance. This paper analyzes and summarizes the research progress of small-scale CO2 gas-liquid two-phase expanders. It is found that replacing the throttle valve with a CO2 expander in the cycle can effectively improve refrigeration efficiency. The cooling and heating efficiency of the cycle is 6.9% and 4.6% higher than that of the R134a cycle, and 25.76% and 16.17% higher than that of the cycle with a throttle valve, respectively. The higher the isentropic efficiency of the CO2 expander, the greater the system efficiency. As long as the isentropic efficiency of the expander is greater than 32%, the performance of the system with a CO2 expander is better than that with a regenerator. Different CO2 expanders have different efficiency, leakage, and friction loss due to their different structures. Piston type, rotor type, and other expanders have simple structures, while their leakage loss is relatively large. The efficiency of the sliding vane type, rotary vane type, and scroll type expander has been greatly improved, but their structure is more complicated, leading to more complicated manufacturing and increased production costs. The compression work is supplied to the compressor, increasing the flow rate during the expansion process, which requires designing a CO2 expander with an adjustable expansion ratio. At present, the research of CO2 expanders is basically concentrated in the laboratory, and this technology has not been commercialized yet. Therefore, the future development direction should combine experiments and theory to further study the efficiency improvement of CO2 expanders and the development of key components technology. |
| Key words: transcritical cycle expander expansion work isentropic efficiency leakage CO2 |
