Numerical analysis on drop-drop electrocoalescence behavior under different electric field parameters

Abstract

ABSTRACT As an environmentally friendly and efficient separation technology, electrostatic dehydration is widely used in oil-water separation in water-in-oil emulsions. To investigate droplet coalescence behavior under different electric field parameters, the coalescence of two water droplets in water-in-oil emulsions was numerically analyzed with the proprietary software Comsol Multiphysics. The motion of the interface was captured by the phase field method and microscopic mechanism of electrostatic coalescence in water-in-oil emulsions was determined. According to force simulation, the difference between electrostatic attraction and interfacial tension of two droplets’ proximal-end and distal-end promoted their approach and fusion process. Furthermore, approach time, fusion time, coalescence time, and distal-end distance S were defined to describe the coalescence characteristics under different electric field frequencies, intensities, and waveforms. The drop-drop coalescence effect was more obvious under an electric field frequency of 20–40 Hz, a higher electric field intensity, as well as DC pulse and half-sinusoidal wave. The deformation degree and electric field intensity at the beginning of droplet coalescence had a significant influence on the coalescence velocity. The results obtained provide much knowledge and a theoretical basis for the technology of compact electrostatic coalescers, which is of great guiding significance for performance prediction and structure optimization.