An experimental study on the non-coalescence exhibited by anchored aqueous droplets in oil

The effect of droplet conductivity on electrocoalescence phenomena is studied experimentally for droplet-in-oil system in an anchored drop setup. Phase diagrams representing the coalescence/non-coalescence behaviour under DC electric field are constructed for three different droplet conductivities. Variation in droplet conductivity and separation distance between droplets do not influence critical electrocapillary number. The critical electrocapillary number varies with oil viscosity. Non-coalescence is not observed for low conductivity (1.5 mu S/cm) droplets for entire range of s(0)/R (initial separation gap to radius ratio), therefore cone angle criteria (Bird et al.,2009) does not apply to anchored droplet-in-oil systems. Non-coalescence is observed as bridge vaporization/gas generation due to high current for high s(0)/R in case of moderate conductivity (1244 mu S/cm) droplets and low s(0)/R for high conductivity (89,500 mu S/cm) droplets. In addition to coalescence and non-coalescence events, subsequent events after first non-coalescence are studied and an effort is made to explain and categorize the behaviour under different regimes. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.