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跨临界CO2两相引射器喷嘴扩张段传热的影响分析
冯义博, 何阳, 邓建强
0
(西安交通大学化学工程与技术学院)
摘要:
跨临界CO2引射器主动流入口状态对引射器性能具有显著影响,主动喷嘴壁面传热会改变主动流状态,其对引射器性能的影响有待研究。基于均质平衡模型假设,构建了跨临界CO2两相引射器的CFD模型,模拟研究了喷嘴扩张段传热对引射器性能和流场结构的影响,并分析了对冷凝器出口分流引射膨胀制冷系统性能的影响。研究结果表明:引射器引射系数随喷嘴扩张段热流密度和喷嘴扩张段长度的增大而增大,但在适用热流密度(小于120 kW/m2)下并不明显,引射系数变化范围在1%以内,其影响可以忽略不计;喷嘴扩张段传热对引射器内部流场的影响较小,喷嘴扩张段内流体温度略有升高,引射器出口干度略有增加,喷嘴出口和混合室内混合流的马赫数也略有增加;对于冷凝器出口分流引射膨胀制冷系统,利用引射器壁面传热可以过冷流体,系统COP显著提高,COP最大提升比例为8.89%。总体而言,对引射器主动喷嘴扩张段加热,对引射器性能影响甚微,但对冷凝器出口分流引射膨胀制冷系统的性能有较明显的提高。
关键词:  两相引射器  均质平衡模型  传热  制冷系统  CO2
DOI:
投稿时间:2023-03-31  修订日期:2023-06-08   录用日期:2023-07-31
基金项目:国家自然科学基金(52006160)资助项目。
Analysis of the Influence of Heat Transfer in the Nozzle Divergence Section of Transcritical CO2 Two-phase Ejector
Feng Yibo, He Yang, Deng Jianqiang
(School of Chemical Engineering and Technology, Xi’an Jiaotong University)
Abstract:
The motive flow state in a transcritical CO2 ejector significantly affects its performance. The heat transfer on the wall of the motive nozzle can change the motive flow state, and its effect on the performance of the ejector should be studied. A CFD model of the transcritical CO2 two-phase ejector is constructed based on the homogeneous equilibrium model. The influence of heat transfer in the nozzle divergence section on the performance and flow field structure of the transcritical CO2 two-phase ejector is simulated. The effect of heat transfer on the system performance of using a split ejector at the condenser outlet is analyzed. The results show that the entrainment ratio of the ejector increases with an increase in the heat flux at the nozzle divergence section and the length of the nozzle divergence section. The effect is not obvious and can be ignored under a moderate heat flux, i.e. less than 120 kW/m2 since the entrainment ratio changes within 1%. In addition, the heat transfer in the nozzle divergence section has a slight effect on the internal flow field of the ejector. The temperature of the internal flow in the nozzle divergence section increases slightly, the vapor quality at the ejector outlet rises slightly, and the Mach numbers of the mixed flow at the nozzle outlet and in the mixing chamber increase. In the condenser outlet split ejector expansion refrigeration system, the fluid is subcooled using the ejector, and the coefficient of performance (COP) of the system is significantly improved, with a maximum COP increase ratio of 8.89%. In general, heating the divergence section of the motive nozzle of the ejector exerts minimal effect on its performance. However, it significantly improves the performance of the condenser outlet split-ejector expansion refrigeration system.
Key words:  two-phase ejector  homogeneous equilibrium model  heat transfer  refrigeration system  carbon dioxide

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