竖管内R113降膜流动特性的结构影响研究

Study on influence of structure of vertical tube on flow features of R113 falling film

为了开发适用于有机工质余热发电降膜蒸发装置,采用FLUENT对氟利昂(R113)竖直管内气液两相逆流降膜进行数值模拟,分析了管长、管径和布膜间隙对降膜流动的影响。研究结果表明:在一定喷淋密度下,不同管长、管径和布膜环形间隙时液膜稳定段厚度相等;同时,管径越小,液膜流动越稳定,当小于某个值时,膜厚沿壁面均匀分布,存在最佳降膜管径;液膜波动随着管长增大而增强,管长大于1.2 m后液膜下段出现飞溅而无法湿润壁面;环形间隙越小,液膜波动越强,减小到1.2mm之后R113无法完整成膜。

In order to develop the falling film evaporation device for organic fluid cogeneration, FLUENT was applied to conduct numerical simulation on the flow of gas-liquid two-phase countercurrent falling film in vertical tube, and the influence of tube length, diameter and annular gap of film distribution on the flow of falling film was analyzed. Study results showed： at given spraying density, the film thickness was the same in stabilization stage at various tube length, diameter and annular gap of film distribution; the less the tube diameter was, the more stable the film flowed, and while the tube diameter being less than a certain value, the film distributed evenly on the wall, thus there was an optimal tube diameter for falling film; the fluctuation of film aggravated with the elongation of the tube, and the film bottom splashed and the wall failed to wet completely while the tube length was more than 1.2 m; the less the annular gap was, the stronger the film fluctuated, and the film was not complete while the annular gap was less than 1.2 mm.