Abstract
Active enhancement of supercooling is one of the promising techniques for cryopreservation. The object of this paper is to study the effects of ultrasonic vibration on heterogeneous ice nucleation on solid surface. In the experiments, water in a tube was cooled at constant cooling rate with ultrasonic vibration at frequency of 1MHz. Two types of ultrasonic vibration; (a) amplitude-regulated vibration and (b) amplitude-modulated vibration were tested by varying ultrasonic power. As the results, supercooling degree at initiation of nucleation increased slightly by applying ultrasonic vibration, since surface-heating effect due to absorption of acoustic energy decreased nucleation area. The weak enhancement of supercooling by periodic variation of sound-wave amplitude was also found.
