不平等電界下における極低温液体中の熱気泡挙動の解析

抄録

The behavior of bubbles in cryogenic liquids under non-uniform fields is studied analytically. A plane-to-cylinder with/without fins is given as an electrode system for producing non-uniform fields. The results show that the bubbles near the tip of high stress electrode like a triangular fin are blown away by the gradient force before breakdown and the force acting on the bubble produces more than an acceleration of 1, 000G, but those trapped in the groove between fins are pressed by the Maxwell stress in the direction of the groove bottom. This suggests that the heat transfer is promoted near the fin top while at the bottom of the groove the nucleate boiling turns to the local film boiling by the voltage application and the heat transfer is reduced there. In a plane-to-cylinder without fins, a spatial region balancing the gradient and gravitational forces appears even if the applied voltage is much lower than the breakdown one and a vapor column bridging between electrodes is believed to be formed in that region. However the vapor column may not seriously affect the breakdown voltage because its formation occurs away from the shortest gap.