Abstract Vertical falling film with low Reynolds number (Re) is widely used, but the influence of surface waves on mass transfer is still unclear. This paper theoretically described the wave structure along the flow direction, and evaluating the enhancement on mass transfer during halide-solution/air absorption. The effects of flow viscosity, surface tension gradient, liquid/air convective heat transfer, film thickness and flow distance are considered. Model validation were performed by comparing with the data from literatures and our experiments. For practical use, empirical correlations of wavelength and amplitude are provided, using Re, Marangoni and Nusselt numbers as variables. Wavelength increases proportionally with liquid Re, and amplitude mainly increases with the flow distance. When Re increases from 20 to 60, wave amplitude and wavelength increase by 10% and 40%. The enhancement effect is determined by the wavelength and frequency, and is more obvious under conditions of large liquid concentration or small liquid Re.

中文翻译：

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垂直低Re降膜的空间域表面波建模及卤化物溶液/空气吸收传质增强

摘要 低雷诺数（Re）垂直降膜被广泛应用，但表面波对传质的影响尚不清楚。本文从理论上描述了沿流动方向的波结构，并评估了卤化物-溶液/空气吸收过程中对传质的增强作用。考虑了流动粘度、表面张力梯度、液体/空气对流传热、薄膜厚度和流动距离的影响。通过与文献数据和我们的实验数据进行比较来进行模型验证。为了实际使用，提供了波长和幅度的经验相关性，使用 Re、Marangoni 和 Nusselt 数作为变量。波长随液体 Re 成比例增加，振幅主要随流动距离增加而增加。当 Re 从 20 增加到 60 时，波幅和波长分别增加 10% 和 40%。增强效果由波长和频率决定，在大液体浓度或小液体Re的条件下更明显。