Liquid-liquid dispersions in milli-scale symmetric confined impinging jets

This paper presents the emulsification process of two immiscible liquids and the flow of the droplets in symmetrical confined impinging jets (CIJs) with two 2mm ID outlets. To investigate the complex phenomena, experiments are combined with computational fluid dynamics (CFD) simulations. Compared to asymmetric CIJs with only one outlet, symmetrical CIJs demonstrate better emulsification performance at high flow rates which makes them preferrable for high-throughput processing. CIJs find many applications such as rapid precipitation, crystallization, extraction of metals, and pharmaceuticals. The flow patterns formed during the impingement of a kerosene oil and an aqueous stream were studied for flowrates ranging from 30-90 ml/min with high speed imaging and ultrasound sensors. Drop sizes were measured immediately after the jet impingement zone and further downstream the channel. The CFD approach implemented a model transition mechanism of volume of fluid (VOF) to discrete phase model (DPM). The CFD successfully captured the mechanism of jet break up and droplet formation at the impinging zone. Good agreement on drop size was found between the experiments and the modelling. Drop velocity profiles were also measured by the ultrasound doppler method. The results showed that drop sizes and drop velocity profiles are significantly influenced by the Reynolds number of the continuous phase.