混合冷剂在竖直矩形小通道内上升流沸腾换热模拟

Simulation of Boiling Heat Transfer on Upward Flow of Mixture Refrigerant in Vertical Rectangular Minichannel

  • 摘要: 为研究板翅式换热器流道内混合冷剂沸腾换热规律,建立了竖直矩形小通道内混合冷剂沸腾换热数学物理模型;基于理论推导的汽液相界面交互深度确定方法,采用CFX双流体模型模拟分析了混合冷剂在竖直矩形小通道内上升流沸腾换热规律,并与文献已有经验关联式进行对比分析. 结果表明:由于混合冷剂物性影响,沸腾换热系数随干度增大而降低;由于对流沸腾和核态沸腾换热机理共同作用,沸腾换热系数随质量流率、热流密度增加而增大;同时,模拟与经验关联式对比结果表明,Lazarek换热关联式计算结果与模拟吻合较好,其误差在±15%以内,将其应用于估算竖直矩形小通道内混合冷剂沸腾换热系数具有较高可靠性.

     

    Abstract: In order to investigate the characteristic of boiling heat transfer for mixture refrigerant in plate-fin heat exchanger, a model was established on boiling heat transfer in vertical rectangular minichannel. Based on the interfacial length scale derived by theory principle, the characteristic of boiling heat transfer was simulated for mixture refrigerant in vertical rectangular minichannel by Euler-Euler model in CFX. The simulation results were also compared with some correlations in literatures. The results show that the boiling heat transfer coefficient decreases with the increase of quality because of the influence of the material property for boiling heat transfer. At the same time, the boiling heat transfer coefficient increases as the mass flow rate and heat flux increase. This is because that the convection boiling and nucleate boiling is main heat transfer mechanism in a vertical rectangular minichannel. The Lazarek's correlation calculations agree well with the simulation results and the error between the simulation results and Lazarek's correlation is within ±15%. These results will provide some constructive instructions in the design of boiling heat transfer characteristics for plate-fin heat exchanger.

     

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