Theory of convective, transient, multicomponent droplet vaporization

The vaporization of a multicomponent droplet in a strong convective gas stream is analyzed, with particular emphasis on the generation of internal circulation through the surface shear and its effects on the internal heat and mass transport processes. It is demonstrated that boundary layers exist in both the gas and liquid phases near the droplet surface over most of its lifetime, and that convection is an important transport mode within the droplet. An approximate analysis for the shoulder region then shows that: the more volatile compounds are always preferentially vaporized; in the liquid the more/less volatile compounds diffuse outward/inward respectively; and the relative rates with which the droplet heats up and conforms to the gas motion are expected to strongly influence the droplet behavior. A more general model, consisting of an exterior potential flow, an interior Hill's Vortex, and boundary layers near the interface, is outlined to study the transient behavior of the droplet.