Simultaneous experimental analysis of concentration and velocity fields in liquid film flows when flowing over microstructured surfaces

微结构表面在工艺设备如填料塔、蒸发器或冷凝器中的应用不仅确保了改善的润湿性，而且还显著增加了形成的液膜中的传质。然而，它还没有完全阐明，以何种方式的微结构影响的动量分布，并随后在液膜流的质量传输。因此，在本研究项目中，研究了单个和多个微结构对具有不同微结构的倾斜板元件上从气流到重力驱动液膜流的传质的影响。为了能够通过实验分析动量分布与气体传输的耦合，将在紧邻微结构的液膜内同时测量被吸收气体组分的浓度场和速度场。为此，将首先实现将用于浓度场测量的平面激光诱导荧光方法与用于通过透明微结构模制件的背面进行速度场测量的立体粒子图像测速法相结合的测量设置。随后，将系统地研究不同气体和液体负载下单个微结构形状的影响以及多个微结构之间距离的影响。计划的测量活动包括单向微结构的溢出（长方体、棱柱体和半圆柱体级）以及双向微结构周围和上方的流动（金字塔，半球和立方体）。因此，该研究项目将为识别和基本理解现象学微观结构影响做出根本性贡献，并为微观结构优化的数值流动模拟验证提供数据库，从而对传质过程的基本理解以及对新颖和最佳结构的设计和开发做出进一步的贡献。

The application of microstructured surfaces in process equipment such as packing columns, evaporators or condensers not only ensures improved wetting, but also significantly increases mass transfer in the liquid film that forms. However, it has not yet been fully elucidated in which way microstructures influence the momentum distribution and subsequently the mass transport within liquid film flows. In this research project, the influence of single and multiple microstructures on the mass transfer from a gas flow into gravity-driven liquid film flows on inclined plate elements with different microstructures is therefore investigated. In order to be able to experimentally analyse the coupling of the momentum distribution with the gas transfer, the concentration field of the absorbed gas component is to be measured simultaneously with the velocity field within the liquid film in the immediate vicinity of the microstructure. For this purpose, a measurement setup combining a planar laser induced fluorescence method for concentration field measurement with stereoscopic particle image velocimetry for velocity field measurement through the backside of transparent microstructure mouldings will be realised first. Subsequently, the influence of the shape of individual microstructures and the influence of the distance between several microstructures will be systematically investigated for different gas and liquid loads. The planned measurement campaigns include the overflow of unidirectional microstructures (cuboid, prism and half-cylinder stages) and the flow around and over bidirectional microstructures (pyramid, hemisphere and cube).This research project will thus make a fundamental contribution to the identification and basic understanding of the phenomenological microstructure influence and provide a database for the validation of numerical flow simulations for microstructure optimisation, thus making a further contribution to the fundamental understanding of mass transfer processes and to the design and development of novel and optimal structures.