THERMOCAPILLARY BREAKDOWN OF SUBCOOLED FALLING LIQUID-FILMS

This investigation explores the mechanism for film breakdown in the case of heat transfer to subcooled, single-component liquid films. Attention is focused on thermocapillary breakdown, resulting from lateral flow diversion induced by a Marangoni effect associated with temperature gradients in the falling film. Combined with a force-balance model for a stable dry patch, an analysis is developed to predict film breakdown. Experiments were conducted with water, 2-propanol, and ethylene glycol, over a film Reynolds number range of 5-1074 and various degrees of subcooling. New data, along with earlier published data for subcooled films, are successfully correlated with the proposed model in terms of a diversion parameter D(t) by the expression D(tc) = 415Re-0.71Pr-0.44. Comparison between the experimental data and the model show an average deviation of 26%, a substantial improvement over existing correlations.