Experimental and theoretical approaches on droplet formation from a micrometer screen hole

The droplet formation process from a micrometer screen hole under crossflow conditions was applied to study the droplet behavior in the high-promising processes of micromixing and membrane emulsification. Three working systems with different interfacial tension were used, and the effects of flow rates and interfacial tension on droplet formation were investigated. To elucidate the influence of systems' properties and flow rates, a theoretical model based on force balance has been developed, in which a parameter of detachment period and a dimensionless number x meaning the drag force torque fraction have been defined to distinguish whether the influence of detachment period should be considered. It was found that the dispersed phase flow rate has little influence on the droplet diameter for the system with large interfacial tension of 51.0 mN/m. And the droplet size can be predicted with the torque balance equation directly. While for the systems with interfacial tension of 1.7 and 8.13 mN/m, respectively, the increase of the dispersed phase flow rate resulted in droplet size increment. Therefore, the effect of detachment period should be considered. Using the theoretical model, the detachment time td can be fitted as a function of x, and the calculated droplet diameters are in good agreement with the experimental values.