The hydrodynamic aspect mechanism of the effect of surfactant on boiling heat transfer

Surfactants have been widely used in various industrial fields. Simply adding a small amount of surfactant can greatly enhance the boiling heat transfer of water, which can improve the performance of heat exchanger and has great application prospects in industry, but its mechanism is not fully understood. Many possible factors have been proposed, but their relative importance remains to be examined. In this paper, the possible mechanisms of surfactant effects proposed in the literature are revisited, and their impacts are discussed in depth. Combined with the experimental study, it was found that when the surfactant concentration was low, the change in boiling performance was mainly due to the non-coalescence of growing bubbles on the wall rather than the change of physical properties of the solution. The underlying reason is that surfactants alter the mobility of the vapor-water interface. At high heat flux, the non-coalescence bubbles form wet foam, making it impossible for bulk water to pass through to wet the heating surface, thereby reducing CHF. At the same time, the immobility of the vaporwater interface also increases the interface resistance, making it more difficult for the vapor to escape from the wall.