Dynamic processes occurring during the spreading of thin liquid films produced by drop impact on hot walls

When liquid drops impinge on a wall heated up above the boiling temperature of the liquid, bubbling and convection are observed in the emerging film w hich spreads along the wall. Experimental investigations of these processes and of the connected evaporation of the liquid are aimed at an improved un derstanding of the underlying mechanisms important for many technical appli cations. Typical Weber numbers of the impinging drops were varied between 5 0 and 700, the temperature of the polished aluminium wall between 70 degree s C and 400 degrees C, i.e., above the boiling temperature of ethanol used in the experiments. The growth rate of bubbles, their maximum diameter and their collapse as well as the formation and destruction of convection cells in the liquid film were recorded and analysed. (C) 1999 Published by Elsev ier Science Inc. All rights reserved.