Applied Laser Technology, Faculty of Engineering Technology, University of Twente, Enschede, The Netherlands.
Langmuir. 2012 Oct 23;28(42):15106-10. doi: 10.1021/la302181f. Epub 2012 Oct 8.
Droplets are able to levitate when deposited over a hot surface exceeding a critical temperature. This is known as the Leidenfrost effect. This phenomenon occurs when the surface is heated above the so-called Leidenfrost point (LFP), above which the vapor film between the droplet and hot surface is able to levitate the droplet. Such a critical temperature depends on several factors. One of the most studied parameters has been the surface roughness. Almost all of the experimental studies in the literature have concluded that the LFP increases with the roughness. According to these results, it seems that the roughness is detrimental for the stability of the vapor film. In contrast with these results, we present here a micropatterned surface that significantly reduces the LFP. The temperature increase, relative to the boiling point, required to reach the LFP is 70% lower than that on the flat surface. The reasons for such an effect are qualitatively and quantitatively discussed with a simple semiempirical model. This result can be relevant to save energy in applications that take advantage of the Leidenfrost effect for drop control or drag reduction.
当液滴沉积在超过临界温度的热表面上时，它们能够悬浮。这被称为莱顿弗罗斯特效应。当表面被加热到所谓的莱顿弗罗斯特点（LFP）以上时，液滴和热表面之间的蒸汽膜能够使液滴悬浮，这种现象就会发生。这种临界温度取决于几个因素。其中一个最受研究的参数是表面粗糙度。文献中的几乎所有实验研究都得出结论，LFP 随粗糙度的增加而增加。根据这些结果，似乎粗糙度对蒸汽膜的稳定性不利。与这些结果相反，我们在这里展示了一种微图案化表面，它显著降低了 LFP。与在平坦表面上相比，达到 LFP 所需的温度升高（相对于沸点）降低了 70%。用一个简单的半经验模型定性和定量地讨论了这种效应的原因。在利用莱顿弗罗斯特效应控制液滴或减少阻力的应用中，这种结果可能有助于节省能源。
