Effect of Insoluble Surfactants in Condensation on a Moving Drop: Solutions for Intermediate Reynolds Numbers

An examination of the hydrodynamics and heat transfer associated with condensation on a moving drop in the intermediate Reynolds number regime (Re = 0(100)) has been carried out. The droplet is taken to be initially contaminated with an insoluble monolayer surfactant material. The drop environment is taken to consist of its own vapor and air. The ambient pressure is taken to be one atmosphere. The formulation entails a simultaneous solution of the quasi-steady elliptic partial differential equations that describe the flow field and transport in the gaseous phase, and the motion inside the liquid drop. The heat transport inside the drop is treated as a transient process. A numerical procedure based on the hybrid difference scheme has been employed. The surface tension gradient force induced by the surfactant and the shear stress from the relative motion between the droplet and its outside velocity field are evaluated. Results have been provided for the interface velocity, drag, surface vorticity, external and internal flow structure, surfactant concentration along the droplet surface, and the Nusselt and Sherwood numbers.