Enhancement of cooling rate during rapid quenching of a thin wire by ultrasonic vibration

Experiments were conducted to study the effect of ultrasonic vibrations on heat transfer during the rapid quenching of thin horizontal platinum wires in subcooled water and ethanol. The frequency of ultrasonic vibration was 24 and 44 kHz. The power input to the transducer P ranged from 0 to 280 W. The measured boiling curve had two minimum-heat-flux points; the first (named the Ml point) corresponded to the onset of significant liquid-solid contact. For P ≤ 20 W, the wall superheat at the M1 point increased considerably with increasing P. The heat flux was not much affected by the ultrasonic vibrations until the M1 point was reached. After the M1 point, the heat flux increased significantly with increasing P. The effect was more significant for v = 24 kHz. Distributions of the sound pressure and the cavitation intensity were also measured and their effects on the heat transfer characteristics are discussed.