水平异型管外加装排液板降膜流动数值分析

Numerical Analysis of Falling Film Flow Outside a Horizontal Shaped Circular Tube with a Drainage Strip

液膜热阻是影响水平管外降膜流动传热的主要因素之一,采用加速排泄管外液体及减薄液膜厚度的方法可以使其换热加强。通过建立底部加装排液板的异型管物理模型,采用fluent软件中的VOF模型对其管外降膜流动进行了二维数值模拟,来研究排液板对水平异型管外的降膜流动与传热的影响。并比较了模拟得到结果与文献中的实验数据,变化趋势吻合较好。结果表明:加装排液板的异型管较其光管的平均液膜厚度减薄,管壁的局部Nu数增大,表明排液板可以加速排液,有助于强化传热;蛋形管具有比滴形管更好的排液性能,加装排液板后排液效果更加显著。

Liquid film resistance is one of the main factors which influence the falling flow heat transfer of horizontal tube. It can be used to enhance the heat transfer by accelerating drainage and reducing the thickness of the liquid film.In order to study the effect of the drainage strip on falling film flow and heat transfer outside a horizontal shaped tube,a physical model of special pipe with a drainage plate at the bottom was established and the VOF model of fluent software was used to two-dimensional numerical simulate it. The numerical simulation results were in good agreement with literature experimental data. The results are as follows. Compared the shaped circular tube with a strip with it without a strip,the average film thickness is thinner and the local Nu number is greater. It is showed that the drainage plate can accelerate drainage and reduce the thickness of liquid film,which helps to enhance the heat transfer. The ovalshaped tube has better drainage performance than the drop-shaped tube,and the effect of drainage with the drainage strip is more significant than before.