Kinetic Modelling of Droplet Heating and Evaporation

Abstract

The validity of the assumption that both liquid and gas phases can be treated as a continuum, used in the previous chapters, is questionable when the interface between liquid and gas is modelled, even when the gas pressure is well above atmospheric. The chapter starts with a review of early kinetic models of droplet evaporation. Then more rigorous models, using numerical solutions to the Boltzmann equations for vapour and air, are described. Two regions above the surface of an evaporating droplet are considered: the kinetic and hydrodynamic regions. Vapour and air dynamics in the first region are described by the Boltzmann equations, while the conventional hydrodynamic approach is used in the second region. Collisions between molecules are assumed to be inelastic in the general case. The evaporation coefficient is estimated using molecular dynamics analysis of n-dodecane molecules, based on the united atoms model. The applicability of quantum-chemical models to finding this coefficient is investigated.