外波纹管管外降膜流动过程液膜厚度及速度分布特性

Liquid Film Thickness and Velocity Distribution Characteristics of Falling Film outside the Outer Bellows

针对外波纹管管外降膜流动过程,采用实验结合数值模拟的方法,考察了液体喷淋密度、管间距和管径变化对液膜厚度周向分布的影响,并与光滑管进行了比较,同时分析了外波纹管管外液膜速度分布特性。结果表明:光滑管外液膜厚度由上至下沿周向呈先减小、后增加的趋势,在90°～120°之间液膜最薄;外波纹管去除波纹间凹槽内的液体后,波纹外的液膜厚度数值及其周向分布规律与相同直径的光滑管相似,周向平均液膜厚度随着液体喷淋密度的增加、管间距及管径的减小而增大;液膜沿周向分布的均匀程度及流动速度大小均与液膜厚度有关,波纹外液膜沿周向分布的不均匀性随着液膜厚度的增加而增加,气液界面处的液体速度沿周向分布规律与液膜厚度分布规律相反;相邻两波峰间凹槽内的液体存在局部循环流动。

Experimental study and numerical simulation are used to investigate falling film flow outside the outer bellows.The effects of liquid spray density,tube spacing and tube diameter on the distribution of liquid film thickness has been studied and compared with the smooth tube.At the same time,the velocity distribution characteristics of liquid film outside the outer bellows are studied.The thickness of the liquid film outside the smooth tube decreases from the top to the bottom and then increases.The thinnest liquid film is between 90°~120°.After the liquid in the inter-corrugated groove is removed from the outer bellows,the thickness and the circumferential distribution of the film thickness outside the corrugation are similar to those of the smooth tube with the same diameter.The average liquid film thickness in the circumferential direction increases with the liquid spray density,while it decreases with the increase in tube spacing and in the tube diameter.The uniformities of the distribution of the liquid film in the circumferential direction and the flow velocity are related to the thickness of the liquid film.The nonuniformity of the circumferential distribution of the corrugated liquid film increases with the liquid film thickness.The distribution law of the liquid velocity at the air-liquid interface in the circumferential direction is opposite to the distribution law of the liquid film thickness.The distribution of liquid velocity at the gas-liquid interface in the circumferential direction is opposite to the distribution law of liquid film thickness.Between the two adjacent peaks,there is local circulation of the liquid present in the groove.