Electrocoalescence of drops in a water-in-oil emulsion

Electrocoalescence of water drops in a stagnant water-in-oil emulsion has been studied in a newly developed test cell. An homogeneous electric field was applied across the emulsion volume. It was used to observe drop behaviour in a multi-drop system. The emulsion was made of napthenic oil containing chemically stabilized water drops with size in the range of 5-100 ¿m. Insulated electrodes were used to prevent direct charge injection and electrophoresis. Drop dynamics in the stagnant emulsion was observed by use of a high speed optical camera and high resolution optics. Three parameters were varied systematically: water cut, frequency and amplitude of the bipolar square voltage. Different events during electrocoalescence are described and discussed, including dynamics of both collapse and break-up of drops, chain formation and charge transfer in the emulsion.