Abstract: In order to make further study on the electrohydrodynamic enhancement mechanisms of boiling heat transfer, the shape of boiling bubbles when departing wall in the nonuniform electric field was visually investigated with a high-speed camera. The bubble shape when departing the wall was observed in the nonuniform electric field. The bubbles leaving the wall were basically spherical in shape without the high voltage electric field. The bubbles leaving the wall were elliptical in shape in electric field. When electric field strength was increased, the bubble elongation along the field direction was more obvious. The growth of bubbles was mainly affected by the inertial force and surface tension control without electric field. When electric field was applied, the bubble force increased by the action of electric field force. Electrical stress in the equatorial direction compressed the bubbles in the polar axis direction tensile bubble. Under the action of the electric field, the bubbles were changed from spherical to ellipsoidal in shape. As the field strength increased, the bubble by electrical stress increased, the bubble detachment wall along the field direction of elongation became more obvious. When the voltagewas applied, the bubble detachment frequency increased with the field strength. When the electric field intensity was at 1.4 kV/mm, the bubble detachment frequency was as 1.85 times higher, compared to the situation without electric field. The experimental results showed that electric fields had obvious effects on the behavior of the bubbles.

Key words: electrohydrodynamic, bubble, nonuniform electric fields

摘要： 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非均匀电场作用下的生长过程进行了可视化实验研究，实验观察到非均匀电场作用下汽泡脱离壁面时的形态。当没有施加高压电场时，汽泡脱离壁面时基本上呈球形形状；而外加电场后，汽泡脱离壁面时呈椭球状，而且随着场强的升高，汽泡脱离壁面时汽泡沿场强方向的伸长更加明显。这是由于未加电场时，汽泡的长大主要受惯性力和表面张力的支配。外加电场后，汽泡的受力增加了电场力的作用，电应力在赤道方向压缩汽泡，在极轴方向拉伸汽泡。在电场作用下，汽泡由近似球形形状变成了椭球形形状。随着场强的增大，汽泡所受的电应力加大，使得汽泡脱离壁面时沿场强方向的伸长更加显著。施加电压后，汽泡脱离频率随着场强的增大而增大，当电场强度为1.4 kV/mm时，汽泡的脱离频率为不加电压时的1.85倍。研究结果表明，电场对汽泡的行为有显著的影响作用。

关键词: 电水动力学, 气泡, 非均匀电场