Numerical simulation of gas-liquid interface evolution for flow and condensation in square microchannel

doi:10.11949/j.issn.0438-1157.20171309

Abstract

Abstract:

Based on the fluid volume approach, the gas-liquid interface evolution for R32 flow and condensation in a square microchannel with 50 μm hydraulic diameter is studied. Annular, injection flow, bubbly flow and shrinking bubbly flow are simulated successively. Because of the gas-liquid interface curvature variation along the circumferential direction of channel, the existing surface tension generated transverse pressure gradient in the condensate film, which forces the condensate towards the corners and thins the condensate film at the middle of the wall of channel. A mechanism for the occurrence of injection flow dominated by the surface tension force and interface viscous force is proposed based on the minimum potential energy theory. The interface fluctuations on the annular flow upstream are induced by injection flow at low mass flux, and grow up gradually under interface viscous force which is different from the mechanism of “flow pattern transition at high mass flux being induced by interface fluctuations which grow up while flowing downstream”.

Key words: condensation, microchannel, injection flow, interfacial fluctuation

摘要：

基于VOF模型，模拟了R32在水力直径为50 μm的方形微通道内流动凝结时的气液两相流型演进过程，模拟涉及的流型包括环状流、喷射流、泡状流和收缩泡状流。模拟结果显示，由于沿通道周向气液界面存在曲率差异，凝结液内部存在表面张力导致的横向压力梯度，驱使凝结液流向通道壁面拐角处，减薄通道壁面中部液膜厚度。基于势能最小原理，解释了表面张力与界面黏性力主导的喷射流形成机理。小质量流率时，喷射流诱发环状流上游气液界面波动，界面波动在界面黏性力的作用下逐渐生长。这与大质量流率时，流向下游并逐渐生长的界面波动导致流型转换的机理不同。

关键词: 凝结, 微通道, 喷射流, 界面波动

CLC Number:

TQ124

WU Chunxu, LI Junming. Numerical simulation of gas-liquid interface evolution for flow and condensation in square microchannel[J]. CIESC Journal, 2018, 69(7): 2851-2859.

吴春旭, 李俊明. 方形微通道内流动凝结时气液相界面演进过程的数值模拟[J]. 化工学报, 2018, 69(7): 2851-2859.

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