Enhancement of nucleate pool boiling heat transfer with surfactant

Abstract

Nucleate boiling is the preferred mode of boiling. An experimental setup for studying nucleate pool boiling of water with surfactant additive is developed. Sodium oleate is used as surfactant additive. Saturated nucleate pool boiling of both water and water with sodium oleate on a horizontal cylindrical heater surface has been investigated experimentally. Cartridge type electric heater with provision of surface temperature measurement is employed for heat generation. Change of heat flux with wall superheat is measured and change of heat transfer coefficient with wall superheat is calculated. The experimental results show that a small amount of surfactant enhances the heat transfer coefficient significantly. At low surfactant concentrations, heat transfer coefficient increases with increasing surfactant concentration in water. The maximum heat transfer enhancement is found to be at 250 ppm of sodium oleate solution. By adding more surfactant to water, heat transfer coefficient is found to be lowered. Surface tension of different concentration of sodium oleate solutions is measured. It is observed that the maximum heat transfer coefficient is obtained at a surfactant concentration that corresponds to the critical micelle concentration (cmc) of the surfactant/water solution.