EFFECT OF DISPERSED WATER DROPLET SIZE IN MICROEXPLOSION PHENOMENON FORWATER IN OIL EMULSION

In this work, an experimental study is carried out to optically investigate the behavior of a bicomponent emulsion under strong heating. The role of the inner features of the emulsions on the microexplosion phenomenon is quantitatively evaluated. When a water in oil (W/O) emulsion is quickly heated, the internal water droplets do not vaporize exactly at the boiling point, but rather after a permanency in a metastable state. Then, the growth of steam nuclei leads to a vigorous expansion. The energy released in this stage breaks the molecular bonds of the surrounding oil, resulting in a fragmentation into numerous and smaller droplets. This physical phenomenon is called microexplosion. The main objective of this work is to study the influence of the dispersed water droplet size of W/O emulsions in the fragmentation effect after the microexplosion. A high-speed visual technique is used to achieve this goal. Emulsions were prepared by using commercially available sunflower oil with high water content (25−35%) and surfactant (Span83). With the Leidenfrost effect device, a single droplet was isolated on a hot surface, and accurate images of the phenomenon were recorded. The results, obtained after the postprocessing of the images, show the existence of an optimal condition related to the feature of the emulsions, resulting in a fine, homogeneous, and rapid propagation of the fragmented oil front.