The basic processes leading to coalescence of small droplets of conduc
ting water dispersed in an insulating liquid are examined in the case
of an emulsion flowing between two coaxial cylindrical electrodes and
subjected to an electric field. The formula giving the interaction for
ce between two droplets and the equation governing the evolution of a
polydispersed emulsion are first recalled. Expressions are derived for
the coalescence rate when retaining only the field induced interactio
n between droplets and the characteristic coalescence time is estimate
d. Finally it is proposed that the shear rate plays the major role in
bringing the droplets into contact.