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arXiv 2209.07784physics.flu-dyn
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加热柱上的液滴碰撞和Leidenfrost动力学

Droplet impact and Leidenfrost dynamics on a heated post

Junhui Li, Patricia Weisensee

摘要:

本研究探讨了液滴撞击加热毫米柱的流体破碎和莱顿弗罗斯特动力学。使用高速光学和红外成像,我们调查的液滴寿命,破碎和沸腾模式,以及不同的基板的冷却性能。与平坦基板相比,柱基板导致更短的液滴寿命和高20°C的莱顿弗罗斯特温度,这归因于沿着柱的高度的混合沸腾模式和额外的钉扎。对于低于莱顿弗罗斯特点的温度,在核沸腾状态下,后基板也提供了比其平坦对应物更大的最大温度下降。增强的冷却能力可以归因于更好的液滴钉扎和扩大的液滴-基板接触面积。在倾斜表面上的冲击中,立柱的卓越冷却性能变得尤为明显,立柱成功地防止了液滴的滚动和反弹,使最大局部温度下降增加了51%至180%。有趣的是,在略高于莱顿弗罗斯特点的温度和韦伯数的一个相对较窄的范围内,后基板上的液滴反弹,而不是打破了由于惯性,毛细管和气泡(薄膜)动力学的复杂的相互作用。总的来说,研究结果表明,一个大尺度结构增加莱顿弗罗斯特温度,并提高液滴破碎和界面传热效率在非等温液滴的影响。

英文摘要:

This study experimentally explores fluid breakup and Leidenfrost dynamics for droplets impacting a heated millimetric post. Using high-speed optical and infrared imaging, we investigate the droplet lifetime, breakup and boiling modes, as well as the cooling performance of different substrates. The post substrate leads to a shorter droplet lifetime and a 20°C higher Leidenfrost temperature compared to a flat substrate, attributed to mixed boiling modes along the height of the post and additional pinning. For temperatures below the Leidenfrost point, in the nucleate boiling regime, the post substrate also provides a larger maximum temperature drop than its flat counterpart. The enhanced cooling capacity can be attributed to better droplet pinning and an enlarged droplet-substrate contact area. The post's superior cooling performance becomes especially clear for impact on an inclined surface, where the post successfully prevents the rolling and bouncing of the droplet, providing a 51% to 180% increase in the maximum local temperature drop. Interestingly, at temperatures slightly above the Leidenfrost point and for a relatively narrow range of Weber numbers, droplets on the post substrate rebound rather than break up due to a complex interplay of inertial, capillary, and bubble (thin film) dynamics. Overall, the findings show that a large-scale structure increases the Leidenfrost temperature and enhances droplet breakup and interfacial heat transfer efficiency during non-isothermal droplet impact.

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