The Effect of Gravity on the Stability of an Evaporating Liquid Film

Evaporation of a Dichloromethane liquid film is explored with an evolution equation describing film dynamics. The film is subject to different initial conditions, smooth and uniform random perturbation. Two different gravity environments (Earth and zero gravity) and two different domain shapes (square and rectangular) have been used. The occurrence of long wave instabilities affecting film dynamics is noted in each of these cases. The evaporating Dicholormethane liquid film is destabilized via long wave instabilities in zero gravity. The thermocapillary patterns formed due to long wave destabilization show a coupling to the initial conditions and domain shape. A criterion for the occurrence of long wave instabilities based on the growth rate of perturbations is described. This equation considers a non-stationary film thickness. It predicts that long wave instabilities are always present in zero gravity environments with a growth rate that increases as the film thickness decreases due to evaporation. Our equation for growth rate of long wave instabilities may be used as an engineering design tool to confine operating parameters of zero gravity heat transfer equipment, that include or harness phase change, to safe limits.