Behavior of water droplets on insulator surfaces submitted to DC voltage-coalescence

This paper aims at studying the behavior of water drops deposited on dielectric composite insulating surfaces under DC voltage stress. Experiments were conducted on the coalescence of pairs of sessile water droplets. It particularly analyzes their behavior depending on their size, conductivity and location with respect to electrodes as well as the hydrophobicity of insulator. The conditions for coalescence as well as the discharges activities were also investigated. The critical electric fields corresponding to the instability of water droplets were also determined. The results obtained show that the coalescence rate depends mainly on three parameters: the droplets location on the insulating surface, the droplets volume and the distance between droplets. Drop-drop coalescence produces larger drop which are more sensitive to electric field. Large drop easily deforms, enabling electric current to flow between both electrodes. The magnitude of the current during the coalescence process increases while droplets are approaching together.