Kinetics of Drop Breakage and Drop-Drop Coalescence in Turbulent Flow

Abstract

Emulsions are disperse systems in which one liquid is dispersed in the form of small droplets within another (immiscible) liquid. These droplets are with typical size range between several hundred nanometers and several millimetres. Many everyday consumer products are emulsions, such as many foods, pharmaceutical drugs and paints. Emulsions play also an important role in various technological processes, such as extraction and water purification from organic contaminants. The size of the dispersed drops in these systems is of crucial importance for their properties and for their efficiency upon application.The disruption of big droplets in smaller ones usually occurs in so-called turbulent flow. The latter flow is generated by passing the two immiscible liquids through a device with special geometry, called "homogenizer", with a high linear speed. Usually, the liquids are forced to make multiple passes through the homogenizer, as smaller and smaller drops are formed after each pass.The size of the droplets after emulsification depends on two opposite processes: drop breakup leading to formation of several smaller drops from a larger one, and drop-drop coalescence leading to formation of a larger drop from two smaller drops. In the general case, the