Abstract: The Kelvin Helmholtz instability of phase change interface during filmwise flow condensation in a vertical small diameter tube is studied by means of energy consideration. Based on the rules that the interfacial waving comes from the balance of various forces doing work on the two phase flow system, the mechanism for the effect of the correlating factors on the stability of condensate film is to be explored in detail. The results indicate that, with decreasing tube diameter,gravity and vapor quality,Bernoulli effect and surface tension on vapor liquid interface may exert more obvious influence on condensate film waving,and hence,increase the instability of the film. Condensation and surface tension on the tube wall would stabilize the film,while the film becomes instable only in a certain range of disturbing wavelength. The results of this paper are helpful in understanding the film instability and the transition of flow pattern during flow condensation in a small diameter tube.

摘要： 从能量分析的角度入手 ,研究细竖圆管内流动凝结过程中各作用因素对凝结液膜波动稳定性的影响 ;分析了管径、重力加速度、干度、表面张力、扰动波长以及相变等因素对液膜波动的作用机理 所得结果将有助于探讨细竖管内流动凝结液膜的波动规律 ,加深对流型的转换和不连续流动成因的理解