Abstract: A novel method using ultrasound is introduced for frost suppression on cold flat surface.The dynamic behavior of water droplets dropped on aluminum surface subjected to 20 kHz and 50W ultrasonic vibration was visually studied.The transient processes of deformation,spreading and atomization of water droplets on aluminum surface due to ultrasonic vibration were recorded.The experimental results indicate that the intense disturbance first occurs in the water droplet subjected to instantaneous incentive due to the effect of ultrasonic vibration and then the droplet deforms and spreads.When the liquid film thickness decreases to a critical value,the water droplet instantaneously atomizes.The interfacial shear force generated by ultrasonic mechanical effect and the high pressure impact induced by ultrasonic cavitation might be respectively the dominant factor for droplet deformation and atomization.The results preliminarily show that the ultrasonic vibration can instantaneously atomize the water droplet on aluminum surface in the initial stage of frosting,which provides a possibility for effective frost suppression on cold surface.

Key words: ultrasonic vibration, water droplet, deformation and spreading, atomization, cavitations

摘要： 介绍了一种超声波抑霜新方法。对频率20 kHz,功率50 W的超声波作用下铝表面液滴的动态行为进行了可视化观测。记录了超声开启瞬间液滴变形-铺展-雾化的全过程。试验结果发现,超声作用时,铝表面上的液滴首先产生剧烈扰动,继而变形、铺展。当液膜厚度减小到一临界值时,液滴瞬间雾化。超声机械作用产生的界面剪切力以及空化作用产生的高压冲击分别可能是诱发液滴变形和雾化的主要因素。结果初步表明,高频超声振动能够瞬间除去铝平板表面作为结霜初始阶段的液滴,为冷表面有效抑霜提供了可能。

关键词: 超声振荡, 液滴, 变形和铺展, 雾化, 空穴