CFD aided investigation of single droplet coalescence

• Published in: Chinese journal of chemical engineering 2016-02, Vol.24 (2), p.249-252
• Main Authors: Gebauer, Felix, Hlawitschka, Mark W., Bart, Hans-Jörg
• Format: Article
• Language: English
• Subjects: CFD; Coalescence; Film drainage; Parameter estimation; 单液滴; 合并; 数值模拟; 模型系统; 测试系统; 相互作用; 计算流体力学模拟; 计算流体动力学
• ISSN: 1004-9541; 2210-321X
• DOI: 10.1016/j.cjche.2015.07.024

This article describes the development of a coalescence model using various CFD work packages, and is validated using as toluene water model system. Numerical studies were performed to describe droplet interactions in liq- uid-liquid test systems. Current models use adjustable parameters to describe these phenomena. The research in the past decades led to different correlations to model coalescence and breakage depending on the chemical sys- tem and the apparatus geometry. Especially the complexity of droplet coalescence requires a detailed investiga- tion of local phenomena during the droplet interaction. Computational fluid dynamics （CFD） studies of single droplet interactions were performed and validated with experimental results to improve the understanding of the local hydrodynamics and film drainage during coalescence. The CFD simulations were performed for the in- teraction of two differently sized droplets at industrial relevant impact velocities. The experimental verification and validation of the numerical results were done with standardized high-speed imaging studies by using a spe- cial test cell with a pendant and a free rising droplet. An experimental based algorithm was implemented in the open source code OpenFOAM to account for the contact time and the dimple formation. The standard European Federation of Chemical Engineering （EFCE） test system toluene/water was used for the numerical studies and the experimental investigations as well. The results of the CFD simulations are in good accordance with the observed coalescence behavior in the experimental studies. In addition, a detailed description of local phenomena, like film rupture, velocity gradients, pressures and micro-droplet entrainment could be obtained.