Charge and mass flux in the radial electric field of an evaporating charged water droplet: an experimental analysis

In the electrostatic application of pesticide sprays, charge retention by evaporating droplets in transit to deposit surfaces is a limiting problem. The possible charge loss via evaporative mass transfer and the possible alteration of evaporation rate caused by the presence of the droplet surface charge were experimentally investigated. For studies of evaporation from a charged 3 mm diameter water droplet conducted as a function of droplet potential (-1, -2, and -3 kV) and atmospheric relative humidity (22, 64, and 100%), the current flowing in the radial electric field of the charged evaporating was compared with that flowing in the radial field of a nonevaporating metal sphere to determine if the departing water vapor was electrified. It is concluded that electric charge on evaporating liquid droplets comprising agricultural chemical sprays neither alters the mass transfer rate nor is dissipated by the evaporation