电场中汽泡行为的变化及对沸腾换热的影响

Change of bubble behavior in electric field and its effects on boiling heat transfer

为进一步探索电场强化沸腾换热的机理,利用高速摄像仪对沸腾汽泡在电场作用下的生长过程进行了可视化实验研究,实验观察到电场作用下汽泡生长的动态图像,并对电场作用下汽泡行为的改变对沸腾换热的影响进行了初步分析。研究结果表明:电场作用下汽泡沿场强方向伸长,随着场强的升高,汽泡的脱离长径比增大,脱离体积减小,脱离频率增大。汽泡变形是由于汽泡受到电应力的作用,电应力在赤道方向压缩汽泡,在极轴方向拉伸汽泡,使得汽泡沿场强方向变细变长。由于在电场作用下汽泡行为的变化使得沸腾传热系数和临界热流密度提高。

In order to make further study on the electrohydrodynamic enhancement mechanisms of boiling heat transfer, the growth process of boiling bubbles in the electric field was visually investigated with a high-speed camera. The bubble dynamic growth process was observed in the electric field and boiling heat transfer action influenced by the change of bubble behaviour in the electric field was analyzed. Experimental results showed that the bubble elongated along the direction of the electric field. The bubble＇s aspect ratio and departure frequency increased with increasing electric field intensity, while its departure volume decreased with increasing electric field intensity. The bubble deformation resulted primarily from the effect of electric stress acting on the bubble surface. The bubble became slender and longer along the direction of the electric field because the electric stress compressed the bubble in the equatorial direction and extended the bubble along the axial direction. The boiling heat transfer coefficient and critical heat flux increased due to the change of bubble behavior in the electric field.