Abstract The ultrasonic heat transfer enhancement has a strong dependence on the sound intensity. The higher the local sound intensity is, the better the heat transfer enhancement achieves. Therefore, a focused ultrasonic field is proposed in cavities with elliptical cross-section based on interference criterion and standing wave criterion. To design a cavity with focused ultrasonic field, sound source and heat source are purposely located at the two focus points where sound intensity could be reinforced. There is a compromise between the value of the standing wave coefficient and the time-averaged sound pressure. The profile of heat transfer coefficient is found to be spatially consistent with the simulated time-averaged sound pressure distribution. The cavities with focused ultrasonic field always present larger heat transfer coefficient of natural convection heat transfer than the ordinary ones and the cavity with standing wave coefficient k2 = 8 presents better natural convection heat transfer performance than the cavity with standing wave coefficient k2 = 6. For the sub-cooled boiling heat transfer, bubble plays an important role on the ultrasonic heat transfer enhancement effect. At larger heat flux or smaller sub-cooled temperature, bubbles gather together to form bubble cloud that presents large thermal resistance. The cavitation collapse can disperse the bubble cloud.

中文翻译：

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聚焦超声场下液体中的传热

摘要 超声传热增强对声强有很强的依赖性。局部声强越高，传热增强效果越好。为此，提出了基于干涉判据和驻波判据的椭圆截面空腔聚焦超声场。为了设计一个具有聚焦超声场的腔体，声源和热源特意位于两个可以增强声强的焦点。驻波系数的值与时间平均声压之间存在折衷。发现传热系数的分布与模拟的时间平均声压分布在空间上一致。具有聚焦超声场的腔体的自然对流传热传热系数始终大于普通腔体，驻波系数k2=8的腔体比驻波系数k2=6的腔体具有更好的自然对流换热性能。对于在过冷沸腾传热中，气泡对超声传热强化效果起重要作用。在较大的热通量或较小的过冷温度下，气泡聚集在一起形成具有较大热阻的气泡云。空化坍塌可以驱散气泡云。对于过冷沸腾传热，气泡对超声传热强化效果起着重要作用。在较大的热通量或较小的过冷温度下，气泡聚集在一起形成具有较大热阻的气泡云。空化坍塌可以驱散气泡云。对于过冷沸腾传热，气泡对超声传热强化效果起着重要作用。在较大的热通量或较小的过冷温度下，气泡聚集在一起形成具有较大热阻的气泡云。空化坍塌可以驱散气泡云。