J024024 水の過冷却に及ぼす振幅変調超音波振動の影響([J02402]バイオにおける流れと熱・物質移動(2))

Abstract

A method to actively enhancing supercooling is one of most promising techniques for cryopreservation. The object of this paper is to study the effects of ultrasonic vibration on supercooling of water. In the experiments, water in a circular tube with thermocouple 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 and amplitude-modulated frequency. Regarding the case of amplitude-regulated vibration, the supercooling degree decreases with increasing ultrasonic power. On the other hand, as for amplitude-modulated vibration, weak enhancement of supercooling was found at amplitude-modulated frequency of 20-25kHz. Furthermore, it was indicated that there is optimum value of ultrasonic power for enhancing supercooling degree, since the action of ultrasonic vibration would have two aspects as to promote and reduce nucleation.