Non-coalescence of nonidentical droplets in oil under a DC electric field

Excessive electric field strength causes the droplets to contact but not coalesce, severely deteriorating the oil–water separation efficiency. The investigation of the non-coalescence of nonidentical droplets in oil under a DC electric field is conducted using high-speed photography. The effects of droplet volume ratio and interfacial tension ratio on the characteristics and critical parameters for droplet non-coalescence are systematically explored. The results show the critical electrocapillary number for the non-coalescence of nonidentical droplets and critical contact cone angle decreases as the volume sum increases or the interfacial tension ratio decreases, which is related to the competition between the resultant electric field force and the interfacial tension force. These results contribute to optimizing the operating parameters of the electric coalescer and improving the oil–water separation efficiency.