山形大学紀要(工学) 第11巻 第1号(1970)17-28

“熱伝達に及ぼす超音波振動数の影響"

玉木康夫・江川貞俊・狩野 猛・油川 博




Effect of Ultrasonic Vibration on Heat Transfer to
Water Flowing in Tube

Yasuo TAMAKI, Sadatoshi EKAWA, Takeshi KARINO
and Hiroshi YUKAWA

The effect of ultrasonic vibration on heat transfer to water flowing in tube was investigated using vertical concentric-tube heat exchanger. The frequencies used were 29, 50, 100, and 1500 Kc/sec and the direction of vibration was parallel to the axis of the tube.
The results were expressed as the ratio of average heat transfer coefficient with vibration to that without vibration and were correlated by Sieder-Tate's equation.
The increase in heat transfer coefficient with vibration was about 6% (up to 28%) for 29 and 50 Kc/sec and a little for 100 Kc/sec but no significant change was found for 1500 Kc/sec.
It was found that the effect of vibration per ultrasonic intensity, i.e. (h,-h)/h.I increased with the increase of frequency and showed the maximum value around 40 Kc/sec.
The streak photography was used to gain the insight into the mechanism which caused the heat transfer coefficient to increase with vibration.
The reason for the increase 1n heat transfer coefficient with vibration was that the thermal boundary layer was disrupted by irregular motion of the cavitation bubbles which were formed with vibration in the vicinity of the heated surface.



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