DEPOSITION OF TILL DROPLETS ON A STEEL PLATE - SIMULATIONS AND EXPERIMENTS

Impact and solidification of tin droplets on a flat stainless steel pl ate was studied using both experiments and numerical simulation. In th e experiments, tin droplets (2.1 mm diameter) were formed and dropped onto a stainless steel surface whose temperature was varied from 25 to 240 degrees C. Impact of droplets was photographed, and evolution of droplet spread diameter and liquid-solid contact angle measured from p hotographs. Substrate temperature variation under an impinging droplet was measured. A complete numerical solution of the Navier-Stokes and energy equations, based on a modified SOLA-VOF method, was used to mod el droplet deformation and solidification and heat transfer in the sub strate. Measured values of liquid-solid contact angle were used as a b oundary condition for the numerical model. The heat transfer coefficie nt at the droplet-substrate interface was estimated by matching numeri cal predictions of the variation of substrate temperature with measure ments. Comparison of computer generated images of impacting droplets w ith photographs showed that the numerical model correctly modelled dro plet shape during impact as it simultaneously deformed and solidified. A simple analytical model was developed to predict the maximum spread diameter of a droplet freezing during impact. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.