Experimental investigations of the fluid dynamics in liquid falling films over structured packing geometry

摘要

The objective of this study was to adapt an optical non-invasive measurement methodology for the investigation of the fluid dynamics in thin liquid falling films. The technique should allow to directly observe effects of the surface topology of structured packings on the flow field and film thickness distribution during flow over real packing surfaces. Three component planar velocity vector fields were determined by means of stereoscopic particle image velocimetry. Optical distortion could be avoided by measuring from the back through specially-prepared transparent moldings of packing surfaces which match the refractive index of the liquid. The adapted stereoscopic particle image velocimetry was validated for laminar liquid film flow over a smooth inclined plate. The results for laminar flow over an inclined plate with a tetrahedral micro-structured packing surface indicate an increased exchange of fluid elements over the liquid film height and in the liquid film between microstructures. Furthermore, the technique allowed spatially resolved complex observations of liquid flow behavior in real packing channel geometries. The methodology may be used to attain basic data for validation of numerical studies to improve understanding the geometry effects of complex surface topologies on liquid film flow dynamics and for numerical studies on packing structure optimization. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.