Effect of glycerol on the binary coalescence of water drops in stagnant oil phase

The binary coalescence of water drops forming through capillaries at low inlet flow rates in an immiscible stagnant oil phase was studied and the evolution of the coalescence process was recorded using a high speed video camera. An increase in the inlet flow rate as well as in the drop size was found to increase the time required for coalescence. Interfacial tension was also varied by adding glycerol in the water phase. Although glycerol reduced the interfacial tension, the drop–drop coalescence time decreased in contrast to what has been reported in the literature. Experiments with the oil phase saturated with glycerol demonstrated that the decreased coalescence times could only partly be explained by mass transfer. The reduced water drop coalescence times in the presence of glycerol were also considered to be responsible for the decreased water fraction required for the phase inversion of the organic–aqueous dispersion.