气泡微细化沸腾过程中气泡冷凝破裂现象

Condensation and collapse of bubbles in region of microbubble emission boiling

为了研究气泡微细化沸腾（MEB）时的气泡动力学行为，利用高速摄像仪（Fastcam SA5）观察15～60 K过冷度范围内，直径10 mm加热面上的沸腾过程。通过引入等效半径，分析核态沸腾、膜态沸腾和MEB区域的气泡行为特征。结果表明：MEB发生时的气泡行为，既不同于核态沸腾，也与膜态沸腾明显不同。在MEB区域，加热面上通常会形成一个大的、不规则气泡，但并不会脱离加热面，而是迅速破碎凝结；而且气泡生命周期相对较小，体积变化速率更快。量纲1分析发现，在MEB区域，随着壁面过热度和热通量的升高，气泡凝缩破裂过程受惯性控制影响程度逐渐增加。

To illustrate the bubble dynamics in microbubble emission boiling （MEB）, a high-speed video camera （Fastcam SA5） was employed to observe the boiling phenomena on a heating surface with a diameter of 10 mm at the liquid subcooling of 15-60 K. An equivalent radius was induced to analyze the bubble behavior in different boiling regions. It is showed that the bubble behavior of MEB differs from that of nucleate boiling and film boiling obviously. In the regime of MEB, a large irregular bubble commonly forms on the heating surface and collapses immediately, but not departures from the heating surface. The period of bubble ebullition is shorter, with a faster change rate in volume. A dimensionless analysis shows that the inertia control increasingly dominates the process of bubble collapse with the increase of wall superheat and heat flux.