Abstract

The coalescence kinetics of oil-in-water emulsions in a wide range of properties and flow microfluidic conditions is quantified. The conditions were chosen in order to mimic situations found in industrial processes involving liquid-liquid dispersions. With that aim, a numerical scheme based on population balance equations is proposed, applied, and validated by comparison to microfluidic experiments reported in the literature. A coalescence efficiency model accounting for colloidal and hydrodynamic interactions, and interface mobility is incorporated using the Smoluchowski collision kernel. The latter assures the accurate estimation of the droplet size evolution which governs the interfacial area and rate of mass transfer. Besides, the combined effect of interfacial tension and oil viscosity on the coalescence kinetics is properly quantified with one single fitting parameter. From the kinetics, the estimated coalescence time increases as the shear rate and volume fraction of the dispersed phase diminish. The close agreement of our results with the experimental findings substantiates the accuracy and wider application of the methodology here described as a diagnostic tool beneficial to industrial process design and control. (C) 2019 Published by Elsevier Ltd.