关键词: 超声振荡, 冻结液滴, 冷表面, 温度阶跃, 空化效应

Abstract: Effects of ultrasonic vibration on frozen water droplets on cold plate surface were studied experimentally.The phenomenon of removing frozen water droplets from the cold surface subjected to 20 kHz ultrasonic vibration was visually observed.The instantaneous shedding process of frozen water droplets from the surface was recorded and the variation of internal temperature of cold plate was analyzed.The mechanism of ultrasonic vibration for instantaneous removal of frozen water droplets from the cold surface was discussed.The experimental results indicate that due to the ultrasonic vibration,the frozen water droplet instantaneously falls off accompanying with upspring phenomenon.Meanwhile,the internal temperature jump occurs in the cold plate.The combined action of the shear force from ultrasonic mechanical effect and the impact by cavitation effect may be the main reason for the removal of frozen droplets.The ultrasonic vibration can remove the frozen water droplet instantaneously,which is the base for frosting on cold surface,and thus it is a highly effective defrosting method.

Key words: ultrasonic vibration, frozen water droplet, cold surface, temperature jump, cavitation effect