Study on the Influencing Factors of Droplet Coalescence in a Mixing Tank

Continuous-phase viscosity and interfacial tension are believed to be key factors in droplet coalescence, but their influencing law in a turbulent flow field has never been directly measured until now. In this study, the droplet coalescence frequency was directly measured over a wide range of physical properties by changing the two-phase system in a mixing tank. The experimental results indicated that the coalescence frequency function increased with increasing continuous-phase viscosity and decreasing interfacial tension. The collision frequency function was also measured and found to be independent of the continuous-phase viscosity and interfacial tension, while it was influenced by the rotational speed and droplet diameter. The mechanism of droplet collision in the mixing tank was analyzed based on the flow field, and empirical models of droplet collision and coalescence efficiency were proposed, which agreed well with the experimental results.