水平管降膜厚度分布特性及对传热的影响  

Distribution Characteristics of Falling Film Thickness around Horizontal Tube and Its Influences on Heat Transfer

作　　者：侯昊[1] 毕勤成[1] 马红[1] 

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,陕西西安710049

出　　处：《西南交通大学学报》2011年第6期1013-1018,共6页Journal of Southwest Jiaotong University

基　　金：国家973计划资助项目(2009CB219805)

摘　　要：为了解水平管降膜流动状况,基于气液两相界面的物理特性,在外径为20～32 mm、管间距为10～40 mm、雷诺数为150～800的范围内,应用电导探针法,实验研究了液膜沿水平管周向分布特性,获得了液膜在10°～170°周向范围内的分布参数,分析了这些分布参数对水平管局部传热的影响.结果表明:Nusselt公式对圆管下半周液膜厚度的预测值明显偏大,在不同工况下,最薄液膜出现在周向角为90°～115°的区域内;液膜厚度随管间距的增加而减小,随雷诺数的增加而增大,管径变化对其影响很小;粗糙管壁可以薄化液膜,传热管结垢区域容易引起液膜破裂,导致"干斑"现象发生.According to the physical characteristics of gas-liquid interfaces, the film thickness on the perimeter of a horizontal tube was experimentally studied by a conductance probe method to understand the flow behavior of a falling film. Measurements were conducted under the following conditions： outside diameter D = 20-32 mm, intertube spacing S = 10-40 mm, and film Reynolds number Re = 150 -800. Falling film distributions over a range of circumferential angles from 10° to 170° were obtained and their effects on heat transfer were examined and analyzed. The results indicate that the values predicted by Nusselt＇s theory are larger than the measured values on the lower perimeter of the tube. The minimal values of the film thickness tend to locate at different circumferential angles in the range of 90° to 115° under different operating conditions. The film thickness decreases with the intertube spacing increasing and increases with Re. Moreover, the changes in tube diameter have little influence on the film distribution. The rough outer wall of the tubes can make the film thinner. In addition, the film free-surface is disrupted in the region of scale formation, which facilitates the formation of dry patches on the heat transfer surface.

关 键 词：水平管降膜 液膜厚度 分布特性 电导探针法 传热 

分 类 号：TK124[动力工程及工程热物理—工程热物理]