跨临界二氧化碳双级压缩多联引射制冷系统的实验研究

Experimental Study of Transcritical Carbon Dioxide Two-Stage Compression Multiejector Refrigeration System

摘要

二氧化碳(CO₂)制冷技术因其绿色环保、单位容积制冷量大等优势近年来备受关注．多联引射器的引入对跨临界二氧化碳制冷系统的能效提升具有至关重要的意义．本文设计并搭建了配备多联引射器的跨临界二氧化碳双级压缩制冷系统测试平台,成功获取了双级压缩制冷系统、基于双级压缩的多联引射制冷系统在不同运行工况下的能效变化情况,精确量化了多联引射器对系统性能系数(COP)、制冷量、压缩机耗功等关键参数影响,并分析了多联引射制冷系统能效提升机理,为跨临界二氧化碳多联引射制冷系统进一步研究提供了参考依据与数据支持．结果表明：在本实验边界条件下,二氧化碳双级压缩制冷系统的最高 COP 为 2.62,此时系统最高运行压力为 7.39 MPa；二氧化碳多联引射制冷系统的最高 COP 为 3.13,此时系统最高运行压力为 7.11 MPa. 与双级压缩制冷系统相比,多联引射器的引入对 COP 提升率可达 19.4%,并有效降低系统最优高压压力.

Abstract

Carbon dioxide refrigeration technology has attracted remarkable attention in recent years owing to its advantages,such as environmental friendliness and large refrigeration capacity per unit volume. The introduction of multiejector is of crucial importance for improving the energy efficiency of transcritical carbon dioxide refrigeration systems. In this paper,a test platform for transcritical carbon dioxide two-stage compression refrigeration systems equipped with multiejector was designed and built. The changes in the energy efficiency of two-stage compression refrigeration systems and multiejector refrigeration systems based on two-stage compression under varying operating conditions were successfully obtained. The influence of the multiejector on key parameters such as the coefficient of performance(COP),refrigeration capacity,and compressor power consumption of the systems was accurately quantified. The mechanism for improving the energy efficiency of multiejector refrigeration systems was analyzed,providing a reference basis and data support for further research on transcritical carbon dioxide multiejector refrigeration systems. The results show that under the boundary conditions of this analysis,the maximum COP of the carbon dioxide two-stage compression refrigeration system is 2.62,the maximum operating pressure of the system is 7.39 MPa,the maximum COP of the carbon dioxide multiejector refrigeration system is 3.13,and the maximum operating pressure of the system is 7.11 MPa. In conclusion,compared with the two-stage compression refrigeration systems,transcritical carbon dioxide two-stage compression refrigeration systems equipped with multiejectors can increase COP by 19.4% and effectively reduce the optimal high pressure of the system.

关键词

二氧化碳制冷 / 双级压缩 / 多联引射 / 系统性能

Key words

carbon dioxide refrigeration / two-stage compression / multiejector / coefficient of performance

参考文献

[1] Lorentzen G. Revival of carbon dioxide as a refrigerant[J]. International Journal of Refrigeration, 1994, 17(5):292-301.

[2] Lorentzen G. The use of natural refrigerants:A complete solution to the CFC/HCFC predicament[J]. International Journal of Refrigeration, 1995, 18(3):190-197.

[3] Bodinus W S. The rise and fall of carbon dioxide systems[J]. ASHRAE Journal, 1999, 41(4):37-42.

[4] Kim M. Fundamental process and system design issues in CO₂ vapor compression systems[J]. Progress in Energy and Combustion Science, 2004, 30(2):119-174.

[5] Zhang F Z, Jiang P X, Lin Y S, et al. Efficiencies of subcritical and transcritical CO₂ inverse cycles with and without an internal heat exchanger [J]. Applied Thermal Engineering, 2011, 31(4):432-438.

[6] Llopis R, Sanz—Kock C, Cabello R, et al. Experimental evaluation of an internal heat exchanger in a CO₂ subcritical refrigeration cycle with gas—cooler [J]. Applied Thermal Engineering, 2015, 80:31-41.

[7] Yu B, Yang J, Wang D, et al. An updated review of recent advances on modified technologies in transcritical CO₂ refrigeration cycle [J]. Energy, 2019, 189:116147.

[8] Li Q, Guo X M, Li W G, et al. Experimental investigation on the performance of the transcritical CO₂ two—phase ejector refrigeration cycle [J]. Journal of Refrigeration, 2012, 33(5):15-19.

[9] Zheng L X, Deng J Q. Experimental investigation on a transcritical CO₂ ejector expansion refrigeration system with two—stage evaporation [J]. Applied Thermal Engineering, 2017, 125:919-927.

[10] Kornhauser A A. The use of an ejector as a refrigerant expander[C]// Proceedings of the International Refrigeration and Air Conditioning Conference. Indianapolis,USA, 1990:10-19.

[11] Besagni G, Mereu R, Inzoli F. Ejector refrigeration:A comprehensive review[J]. Renewable and Sustainable Energy Reviews, 2016, 53:373-407.

[12] Liu J R, Liu Y, Yu J L. Performance analysis of a modified dual—ejector and dual—evaporator transcritical CO₂ refrigeration cycle for supermarket application [J]. International Journal of Refrigeration, 2021, 131:109-118.

[13] Li D, Groll E A. Transcritical CO₂ refrigeration cycle with ejector—expansion device [J]. International Journal of refrigeration, 2005, 28(5):766-773.

[14] Elbel S, Hrnjak P. Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation[J]. International Journal of Refrigeration, 2008, 31(3):411-422.

[15] Liu F, Li Y, Groll E A. Performance enhancement of CO₂ air conditioner with a controllable ejector [J]. International Journal of Refrigeration, 2012, 35(6):1604-1616.

[16] Hafner A, Försterling S, Banasiak K. Multi—ejector concept for R—744 supermarket refrigeration[J]. International Journal of Refrigeration, 2014, 43:1-13.

[17] Gullo P, Hafner A, Cortella G. Multi—ejector R744 booster refrigerating plant and air conditioning system integration—A theoretical evaluation of energy benefits for supermarket applications[J]. International Journal of Refrigeration, 2017, 75:164-176.

[18] Haida M, Banasiak K, Smolka J, et al. Experimental analysis of the R744 vapour compression rack equipped with the multi—ejector expansion work recovery module[J]. International Journal of Refrigeration, 2016, 64:93-107.

[19] Smolka J, Palacz M, Bodys J, et al. Performance comparison of fixed— and controllable—geometry ejectors in a CO₂ refrigeration system [J]. International Journal of Refrigeration, 2016, 65:172-182.

基金资助

国家资助博士后研究人员计划资助项目(GZC20241198)