水平单管外混合气体对流冷凝换热的理论研究

Theoretical Research on Convective Condensation Heat Transfer for Mixture Gas on a Horizontal Tube

采用修正的膜模型与Nusselt凝结理论结合的方法,对含湿混合气体自上而下横掠水平管外时的对流冷凝换热机理进行研究,建立了液膜流动和传热模型,进行数值求解并分析了雷诺数、壁面温度及水蒸汽浓度等因素对混合气体冷凝换热的影响。计算结果表明:水管外壁液膜厚度分布很大程度上受气体边界层对液膜剪切力的影响。而局部努谢尔数不同于纯蒸气的的冷凝换热,它受气相热阻的影响很大,其分布状况类似于单相气体管外的对流换热。

This paper studies the mechanism of convective condensation heat transfer on a horizontal tube across which moist mixed gas flows vertically. The models referring to how the liquid film flows and the heat Wansfers on the tube are set up by combining modified film model and Nusselt＇s condensation theory. The effects of Renold Number and wall temperature and water vapor concentration on condensation heat transfer are discussed. The Results predict that the film thickness profile on the tube is influenced greatly by vapor shear force on liquid film. Local Mussier Number depends remarkably on gas phase heat resistance, which is different from pure vapor and is very similar to single-phase gas.