Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

ACTIVE CONTROL OF ICE FORMATION BY UTILIZING ULTRASONIC IRRADIATION

Get access (open in a dialog) DOI: 10.1615/IHTC13.p3.50
10 pages

Abstrakt

A method to actively controlling crystallization is one of promising technique for cryopreservation. The object of this paper is to study the effect of ultrasonic irradiation on ice formation during freezing of biological materials. In the experiments, agar gel was frozen under irradiation of ultrasound at frequency of 28 kHz. The measurements of temperature and the microscopic observation of ice crystals by using fluorescent indicator were carried out. Firstly, the cooling rate of sample augmented according to the increase of the ultrasonic power, since acoustic streaming and flow disturbance due to acoustic cavitation increased. Secondly, it was found that ice structure size decreased with increasing ultrasonic power in case of rapid cooling. Furthermore, the ultrasonically induced effect on freezing was analyzed using local cooling rate defined at freezing front. It was clarified that smaller ice crystals were formed by irradiating ultrasound, comparing with case without ultrasound, under being the same local cooling rate. Therefore, there is effect on ice formation through not only enhancing local cooling rate due to acoustic streaming, but also other relevant phenomena. The mechanism of sonocrystallisation in biological tissue was discussed in relation to ultrasonic power and cooling rate.