Effect of interphase mass transfer on droplet coalescence in agitated liquid–liquid dispersions

Interphase mass transfer is widely recognized as a pivotal driver of droplet coalescence in multi-phase reactors, yet its governing principles have remained unquantified until now. In this study, we directly measured droplet coalescence efficiency in a mixing tank by systematically varying solute species, concentration gradients, mass-transfer directions, and interfacial mass-transfer flux. The experimental results indicate that the coalescence efficiency decreases when the solute is added for two-phase system in equilibrium state. Mass transfer inhibits coalescence when the direction is C → D (continuous phase to dispersed phase), while opposite direction promotes coalescence, and the promoting effect is larger for larger mass transfer flux. The dimensionless number MaPe was introduced to construct modified coalescence efficiency models based on the model in our previous work. The modified coalescence models agreed well with experimental results under mass transfer conditions.