Abstract The interphase mass transfer in a falling film microchannel relies on the liquid-phase mass transfer behavior. Flow in a liquid film is predominantly laminar, and the liquid mass transfer is usually controlled by molecular diffusion. Micro-mixing structures were designed and configured in a double-side falling film microchannel, and the liquid side mass transfer was enhanced by fluid mixing and surface renewal. Computational fluid dynamics approach was used to simulate the falling film flow and mass transfer behavior with and without micro-mixing structures. The impact of the micro-mixing structures on the liquid side mass transfer coefficient was systematically investigated via CO2 absorption experiments in water. The results showed that the fluid flow and mixing was improved by staggered flow mode with micro-mixing structures in the falling film microchannels. Three flow patterns are observed inside the liquid film, including direct flow, cross flow, and vortex flow when the falling liquid film crosses the micro-mixing structures. Both cross flow and vortex flow intensify the surface renewal and turbulence of the liquid film, which is the fundamental reason for the enhancement of the liquid side mass transfer. The experimental results reveal that liquid side mass transfer coefficient in double falling film microchannels with micro-mixing structures is between 3.59 × 10−5 m/s and 5.38 × 10−5 m/s, while it is between 3.35 × 10−5 m/s and 4.82 × 10−5 m/s without micro-mixing structures. The liquid side mass transfer coefficient is increased 7–14% by the configuration of micro-mixing structures. Therefore, a double-side falling film microcontactor with micro-mixing structures not only reduces the contactor size, but also effectively enhances the interphase mass transfer behavior.

中文翻译：

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微混合结构强化双侧降膜微通道液侧传质

摘要 降膜微通道中的相间传质依赖于液相传质行为。液膜中的流动主要是层流，液体传质通常由分子扩散控制。在双侧降膜微通道中设计并配置了微混合结构，通过流体混合和表面更新增强了液侧传质。计算流体动力学方法用于模拟有和没有微混合结构的降膜流动和传质行为。通过在水中的 CO2 吸收实验系统地研究了微混合结构对液体侧传质系数的影响。结果表明，在降膜微通道中采用具有微混合结构的交错流动模式改善了流体的流动和混合。当下降的液膜穿过微混合结构时，在液膜内部观察到三种流动模式，包括直接流、错流和涡流。横流和涡流都加剧了液膜的表面更新和湍流，这是增强液侧传质的根本原因。实验结果表明，具有微混合结构的双降膜微通道的液侧传质系数在3.59×10-5 m/s和5.38×10-5 m/s之间，而在3.35×10-5 m/s之间/s 和 4.82 × 10−5 m/s，没有微混合结构。通过微混合结构的配置，液体侧传质系数提高了 7-14%。因此，具有微混合结构的双侧降膜微接触器不仅减小了接触器尺寸，而且有效地增强了相间传质行为。