Bubble departure diameter in nucleate pool boiling at saturation: Pure liquids and binary mixtures

• A study in nucleate pool boiling at saturation pure liquids and binary mixtures.
• In electrolyte solutions, larger bubbles are generated compared with water.
• In ethanol/water solutions, larger bubbles are generated compared with ethanol.
• In ethanol/water solutions, smaller bubbles are generated compared with water.
• A new model for the prediction of bubble diameter is proposed (±5% Err).

Bubble dynamics is the most important sub-phenomenon, which basically affects the nucleate pool boiling heat transfer coefficient. Previous investigations state that the effect of physical properties of liquid and vapor phases on bubble departure diameter are often conflicting. In this article, extensive new experimental data at atmospheric pressure are presented for bubble departure diameters during saturated pool boiling for pure water, ethanol and various binary mixtures, including ethanol/water, NaCl/water and Na2SO4/water over a wide range of concentrations. For all test fluids, experimental results show that bubble diameter increases with increasing heat flux. Also, experimental results show that bubble detachment diameter increases with increasing electrolyte concentration and decreases with increasing ethanol mass fraction. A new model for the prediction of vapor bubble departure diameter, based on Buckingham theory, in nucleate boiling is proposed, which predicts the experimental data with a satisfactory accuracy.