Bubble coalescence inhibition in volatile solutions at elevated temperatures

Abstract

An experimental study on the effect of liquid temperature on coalescence of bubble pairs in volatile solutions is presented. Alcohols with low molecular mass were used as volatile additives, and the temperature investigated ranged from 25–60 °C. At low temperatures, earlier results showing increases in coalescence percentage with increasing temperature were reproduced. However, by increasing the temperature to a certain value, the coalescence percentage decreased, which is caused by the Marangoni effect induced by solute evaporation from the liquid bulk to the gas bubble. To the best of our knowledge, this phenomenon has not been previously observed. A theoretical model was derived to include the mass transfer induced Marangoni effect in the film drainage process, and the close agreement between theoretical and experimental results confirmed our suppositions. Results may be applied to various fields, especially in direct‐contact evaporators, and support developments in film drainage theory to account for interfacial mass transfer in distillation columns and boiling systems.