Bubble growth in saturated pool boiling in water and surfactant solution

Abstract

The presence of surfactant additives in water was found to enhance the boiling heat transfer significantly. The objective of the present investigation is to compare the bubble growth in water to that of a surfactant solution with negligible environmental impact. The study was conducted at two values of heat fluxes to clarify the effect of the heat flux on the dynamics of bubble nucleation. The bubble growth under condition of pool boiling in water and non-ionic surfactant solution was studied using high speed video technique. The bubble generation was studied on a horizontal flat surface; and the natural roughness of the surface was used to produce the bubbles. We did a quantitative analysis of single bubble growth, in saturated nucleate pool boiling of water, with constant wall heat flux q = 10 and 50 kW/m 2. The captured images showed that the bubble shape is close to axially-symmetric and vertically non-symmetric. At heat flux of q = 10 kW/m 2 the life-time and the volume of bubble growth-rate in surfactant solution did not differ significantly from those of water. The time behavior of the contact angle of bubble growing in surfactant solution is qualitatively similar to that of water. At a heat flux of q = 50 kW/m 2, boiling in surfactant solution, when compared with that of pure water, was observed to be more vigorous. Surfactant promotes activation of nucleation sites; the bubbles appeared in a cluster mode; the life-time of each bubble in the cluster is shorter than that of a single water bubble. The detachment diameter of water bubble increases with increasing heat flux, whereas analysis of bubble growth in surfactant solution reveals the opposite effect: the detachment diameter of the bubble decreases with increasing heat flux.