Dynamic mechanisms of boiling heat transfer enhancement by laser-induced cavitation

A novel boiling heat transfer enhancement method using the laser-induced cavitation bubble has been proposed. The enhancement of boiling heat transfer by the laser-induced cavitation bubble has been studied through two experiments. One is the single boiling bubble experiment, which is investigated using high-speed photography. It was found that the nucleation wall superheat (ΔTwall) reduced to 1.65 K, representing a 10.65 K decrease compared to normal nucleation due to the influence of the cavitation bubble. Three typical boiling modes have been identified and proposed: the single bubble mode, the continuous mode, and the film mode. The first boiling bubble induced by the cavitation bubble exhibits unique dynamic characteristics, with a periodic change in its aspect ratio observed, corresponding to the cavitation bubble oscillation under the influence of the Bjerknes force. In addition, its inertia-controlled growth mode becomes more significant, and its duration is also extended. The departure diameter is also larger than the following bubbles. Another experiment focused on pool boiling to evaluate the effectiveness of laser-induced cavitation bubbles in enhancing heat transfer. The results demonstrate that the heat transfer coefficient was significantly improved at both low and high wall superheats, whereas only limited enhancement was observed at intermediate superheats. Although the heat transfer performance is improved, the critical heat flux occurs at a lower wall superheat.