ON THE ROLE OF MARANGONI EFFECTS ON THE CRITICAL HEAT-FLUX FOR POOL BOILING OF BINARY-MIXTURES

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has bee n quantitatively estimated with a modified model derived from hydrodyn amics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evid ence, accurate mixture properties, and phase equilibrium revealing a c orrelation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid re storing force caused by surface tension gradients. The CHF condition w as determined experimentally for saturated methanol/water, 2-propanol/ water, and ethylene glycol/water mixtures, over the full range of conc entrations, and compared to the model. The evidence in this study demo nstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.