Drop impact on hot plates: contact times, lift-off and the lamella rupture.
Drop impact on hot plates: contact times, lift-off and the lamella rupture.
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DOI：
10.1039/d0sm00459f
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发表时间：
2020-03
期刊：
影响因子：
3.4
通讯作者：
Sang-Hyeon Lee;K. Harth;M. Rump;Minwoo Kim;D. Lohse;K. Fezzaa;J. Je
中科院分区：
文献类型：
--
作者：
Sang-Hyeon Lee;K. Harth;M. Rump;Minwoo Kim;D. Lohse;K. Fezzaa;J. Je
当液滴撞击在加热的基底上时，它可以保持沉积，或者在接触中剧烈沸腾，或者在接触或不接触表面的情况下离开。这种现象被称为莱顿弗罗斯特效应。液体-基材接触的持续时间和面积与热传递以及其他效应（例如腐蚀）高度相关。然而，大多数实验研究依赖于侧视图成像来确定接触时间，并且这些接触时间通常与直到液滴从基板上剥离的时间混合。在这里，我们开发并验证了一种可靠的方法，接触时间测定使用高速X射线成像和全内反射成像。我们举例比较接触和剥离时间的平面硅和蓝宝石基板。我们表明，即使没有形成一个完整的蒸汽层，液滴可以反弹，具有广泛的升空时间。在蓝宝石上，我们发现一个局部最小的提离时间比预期的要短得多，从毛细管反弹在相对较低的温度制度的过渡沸腾/热原子化。我们阐明了相关的潜在机制自发破裂的薄层和后退的接触面积。
When a liquid drop impacts on a heated substrate, it can remain deposited, or violently boil in contact, or lift off with or without ever touching the surface. The latter is known as the Leidenfrost effect. The duration and area of the liquid-substrate contact are highly relevant for the heat transfer, as well as other effects such as corrosion. However, most experimental studies rely on side view imaging to determine contact times, and those are often mixed with the time until the drop lifts off from the substrate. Here, we develop and validate a reliable method of contact time determination using high-speed X-ray imaging and total internal reflection imaging. We exemplarily compare contact and lift-off times on flat silicon and sapphire substrates. We show that drops can rebound even without formation of a complete vapor layer, with a wide range of lift-off times. On sapphire, we find a local minimum of lift-off times that is much shorter than expected from capillary rebound in the comparatively low-temperature regime of transition boiling/thermal atomization. We elucidate the underlying mechanism related to spontaneous rupture of the lamella and receding of the contact area.