In the world of fossil fuels, crude oil is an indispensable source of energy. During the transportation and processing of oil, water-oil emulsions are frequently created. The traditional methods of eliminating these emulsions are based on utilization of high heat, chemicals, and electrical energy to force the emulsion to separate into water and hydrocarbon phases. Recently, microwave and ultrasonic waves have been successfully tested for demulsification of water-oil emulsions. When emulsion is exposed to the microwave field, molecular rotation and ionic conduction cause internal heating due to penetration of electromagnetic waves into the emulsion, resulting in accelerated emulsion separation. Exposing the emulsion to the ultrasonic field causes the water droplets to migrate to pressure nodes of standing ultrasonic wave under the influence of the primary acoustic force. Further coalescence of droplets is due to attractive secondary interdroplet acoustic forces. Two trajectory models are developed to predict the relative motion of water drops subjected to the microwave and ultrasonic fields. The results show that the coalescence under the microwave field is considerably much faster than the coalescence under the ultrasonic field.