Dynamics of surface waves on films falling down horizontal tubes and associated gas absorption

对水平管液膜下落吸收气体的气体吸收器进行了实验和理论分析，并与垂直管气体吸收器的分析结果进行了比较，对水平管光滑液膜下落吸收气体的过程进行了理论分析，假设浓度边界层从管顶开始，沿着光滑表面向管底发展，当管间距小于毛细常数时，液体在管间形成薄片并在管内连续流动，并形成几乎均匀的膜，沿所有管下落。随着管间距的增大，液体从每根管上滴落，并引起大振幅的波，该波在覆盖在下部管上的膜上迅速传播。滴落使下部管上的膜流动更不均匀。滴落引起的波增强，伴随的气体吸收增加50%或更多，在雷诺数Re<30时，对上管进料流施加周期性扰动，可使管间薄层流膜的气体吸收增强约20%。在直径为6 mm的管上观察到Rayleigh不稳定性，并增强了气体吸收。水平管上的液膜流动，液滴完全更新浓度边界层，并在下管顶部形成新的边界层，其气体吸收率大于垂直管上的液膜流动，而滚波对气体吸收有很大的促进作用。

A gas absorber, in which liquid films fall down horizontal tubes and absorb surrounding gas, was experimentally and theoretically analyzed, and the analytical results were compared with those of a vertical-tube gas absorber.Smooth film falling down horizontal tubes and the associated gas absorption were theoretically analyzed, assuming that a concentration boundary layer starts at the top of tube and develops along the smooth surface to its bottom.When the tube spacings are smaller than the capillary constant, liquid forms sheets between tubes and continuously flows in them, and forms nearly uniform films falling down all tubes.With wider tube spacings, liquid drips off each tube and causes the large-amplitude waves which rapidly spread on the film covering the lower tube.The drip makes the films flow more unevenly on lower tubes.The drip-caused waves enhance, the associated gas absorption by 50% or more, compared with the sheet flow between tubes.Imposing periodical perturbations on feeding flow to the top tube enhances the gas absorption of films with the sheet flow between tubes by 〜20% at the Reynolds number Re<30.Rayleigh instability was observed on films covering 6 mm diameter tubes and enhanced the gas absorption. The film flow on horizontal tubes, in which the drip completely renews concentration boundary layers and a new boundary layer starts at the top of lower tube, has larger gas absorption rate than the films falling down vertical tubes on which roll waves greatly enhance the gas absorption.