Parametric Effects on Interface Evolution and Heat Transfer in Droplet Impact on Flowing Liquid Film

Abstract

Interfacial phenomena and heat transfer associated with single droplet impact on a flowing liquid film are studied with three-dimensional simulations. Shear-induced sheet-film contact is detected successfully, governed by both flowing film and droplet velocities. Crown splashing at the downstream position is suppressed significantly, while cooling performance in the downstream crater is poorer than in the upstream crater because of slippage of the impact region along the streamwise direction. Increasing impact velocity and decreasing film thickness result in a very low wall temperature and high heat transfer coefficient because of enhanced convective heat transfer, but the increase in film velocity compromises cooling of the heating surface. Parametric effects of droplet impacting velocity, film thickness, and thermophysical properties on crown upstream and downstream heights in impact on the flowing film are virtually the same as those on the static film, but the unique parameter of film velocity in the former poses a negative effect on crown heights.