The Study Of Drop Coalescence In The Liquid-Liquid Turbulent Dispersions

In the turbulent stabilized liquid-liquid dispersions, the breakage and coalescence process influence the mass transfer, reactions rates and the inter-phase area between two phases. The study of drop diameters and distributions in oil-water dispersion system and the drop size distribution is one of the crucial aspects in chemical engineering and the study of multiphase fluid.The particle size in oil-water dispersions in stirred tank is theoretically and experimentally studied in this paper. Nowadays, Coulaloglou and Tavlarides model is widely used to calculate the breakage and coalescence process coexisting in the system. But, since the dispersion viscosity has not been considered in the Coulaloglou and Tavlarides model, the calculating results different a lot compared to the experimental data in some circumstances. The films between the coalescing drops are divided into three types according to the surface tension exerting on the intervening films, which are fully mobile, partially mobile and immobile. The type of the intervening film is usually predicted before modeling through the physical properties of the system. The dispersion viscosity hasn't been considered in the models of drops with immobile interface since the large dispersion viscosity. Coulaloglou and Tavlarides model assumes the intervening films between colliding drops are immobile, and the drops are assumed as rigid ones, which clearly is a weakness. To overcome the disadvantage, the viscosity effect on coalescence is further considered in the drop deformation and coalescence process in the present model on the basis of Coulaloglou and Tavlarides model.In order to testify the solidification of the modified model, the population balance equation is adopted to calculate the Sauter mean diameters and particle size distributions of the experiments in the literature. The liquid paraffin-water system is experimentally studied in this paper to testify the modified model. The Sauter mean diameters measurement experiment is carried out in the temperature range from 20℃to 60℃and impeller speed from 200r/min to 600r/min. The pictures of the drops are taken by the digital camera and microscope analyzed by the software of Image-Pro. Compared with several systems in the literature, the results show that the modified model predictions are in a better agreement with the experimental data than Coulaloglou and Tavlarides model.