LASER-INDUCED COALESCENCE OF PETROLEUM-IN-WATER EMULSIONS

A petroleum-in-water emulsion is heated by a CW He-Ne laser beam incid ent in the liquid free surface. The resulting temperature distribution creates a centripetal thermoconvective flow which drives the petroleu m droplets to the central hot point. Coalescence of an increasing numb er of petroleum droplets gives rise to the formation of a homogeneous petroleum bulk, A centrifugal stress distribution now grows up in the central bulk as a result of temperature dependence of the interfacial tension of the petroleum-water interface. An equilibrium state between centrifugal and centripetal forces is finally attained and the system remains at rest. The whole sequence is visualized by observation of t he light beam scattered out from the liquid volume. A theoretical mode l explains the main features of the thermoconvective flow, (C) 1998 El sevier Science B.V.