Enhancement of pool boiling heat transfer in water and ethanol/water mixtures with surface-active agent

Surface tension of ethanol/water mixtures is measured over the whole ethanol fraction range and the effect of the surface-active agent on surface tension is also measured in the mixtures, in order to gain basic data related to enhancement of the heat transfer coefficient in water and the mixtures. The boiling heat transfer coefficient, the onset of boiling and the critical heat flux in water and ethanol/water mixtures, with and without the surface-active agent, have been measured on a horizontal fine heated wire at a pressure of 0.1 MPa. The experiment was carried out in the whole range of the ethanol fraction and in a surfactant concentration of 0-5000 ppm. The experiment shows that the coefficients were enhanced in a lower ethanol fraction (C ? 0.5) and in low heat flux which is slightly higher than heat flux at the onset of boiling. It is also found that the enhancement due to the surfactant disappears over 1000 ppm. Finally, we clarify that depression of the surface tension by the surfactant remarkably enhances the heat transfer coefficients in the nucleate pool boiling.