Average Drop Size in a Liquid-Liquid Phase Mixing Vessel

Abstract

When two immiscible liquids are agitated, a dispersion is formed in which continuous breakup and coalescence of drops occur, and a dynamic equilibrium is attained between breakup and coalescence after a certain time. Effects of the volume fraction of dispersed phase, viscosity of liquid, impeller speed and impeller-to-vessel diameter ratio on the average drop size of a dispersion in a mixing vessel are discussed and correlative equations are proposed. It is also found that the dominant process in deciding average drop sizes in a mixing vessel changes from breakup to coalescence when the average energy dissipation rate or the volumetric fraction of dispersed phase is increased. The damping oscillation of a hanging drop on a nozzle in the air was studied theoretically and experimentally. In the experiments, an elongated drop on a brass nozzle by electrostatic force was made to oscillate by removing the electric field instantaneously and the subsequent drop motion was recorded by a high-speed camera. In the theoretical study, the time-dependent drop shape and flow inside the drop were simulated numerically by use of the finite element method. It was found that the experimental results of oscillatory behavior for a hanging drop of aqueous glycerin solution were in good agreement with the calculated ones and that the frequency of oscillation was affected by drop volume, surface tension and nozzle size. © 1987, The Society of Chemical Engineers, Japan. All rights reserved.