Thermal atomization during droplet impingement on superhydrophobic surfaces: Influence of Weber number and micropost array configuration
Thermal atomization during droplet impingement on superhydrophobic surfaces: Influence of Weber number and micropost array configuration
复制标题
DOI：
10.1016/j.ijheatmasstransfer.2020.120559
复制
发表时间：
2021-01-01
影响因子：
5.2
通讯作者：
Maynes, Daniel
中科院分区：
文献类型：
--
作者：
Emerson, Preston;Crockett, Julie;Maynes, Daniel
对液滴撞击不同微观结构的疏水和超疏水表面时的热雾化强度进行了实验研究。在这些情况下，热雾化是液滴沸腾的结果，其中蒸汽气泡向上穿过液滴薄层破裂，导致二次液滴的细喷雾。在120 ℃至320 ℃的表面温度和20至200的韦伯数范围内，研究了光滑的疏水表面和具有相似固体分数但不同柱尺寸的三个后图案化的超疏水表面。雾化强度的趋势，其特征在于使用高速图像处理技术。表面温度，韦伯数和微观结构配置的变化被证明显着影响雾化强度，这些参数被认为是直接联系到三个主要的机制，占雾化动力学在冲击的情况下。这些机制是在撞击液滴的液-固界面处产生蒸气，蒸气通过扩散层破裂，以及蒸气在液滴下方横向逸出。蒸汽产生随着向液滴的热传递的增加而增加，这可以通过增加表面温度或通过液滴润湿增加液体-固体接触来产生。汽相向上通过层片的突升主要取决于层片厚度，层片厚度随韦伯数的增加而减小。最后，当蒸气横向流过微柱阵列时，可发生在液滴下方的蒸气逸出。这被发现是通过增加结构之间的间距增强。这些竞争机制导致热雾化，其通常随着韦伯数的增加和节距的减小而增加。此外，莱顿弗罗斯特点也被发现，增加韦伯数和减少沥青。进行了尺度分析，以探讨通过微柱阵列的蒸汽逃逸阻力对热原子化的影响，并由此产生的缩放描述了实验结果。(C)2020爱思唯尔有限公司保留所有权利。
An experimental study of thermal atomization intensity during droplet impingement on superheated hydrophobic and superhydrophobic surfaces of varying microstructure was performed. Thermal atomization in these scenarios is the result of droplet boiling, where vapor bubbles burst upwards through the droplet lamella, causing a fine spray of secondary droplets. A smooth hydrophobic surface and three post-patterned superhydrophobic surfaces of similar solid fraction but differing post size were investigated over a range of surface temperatures from 120 degrees C to 320 degrees C and Weber numbers from 20 to 200. Trends in atomization intensity were characterized using a high-speed image processing technique. Changes in surface temperature, Weber number, and microstructure configuration were shown to significantly influence atomization intensity, and these parameters are thought to be directly linked to three main mechanisms accounting for atomization dynamics in impingement scenarios. These mechanisms are vapor generation at the liquid-solid interface of the impinging droplet, vapor bursting through the spreading lamella, and vapor escape laterally beneath the droplet. Vapor generation increases with an increase in heat transfer to the droplet, which may be produced by increasing surface temperature or increasing liquid-solid contact through droplet wetting. Vapor bursting upwards through the lamella depends mainly on lamella thickness which decreases with increasing Weber number. Finally, vapor escape beneath the droplet may occur as vapor flows laterally through the micropost arrays. This is found to be enhanced by increasing the spacing between structures. These competing mechanisms result in thermal atomization, which generally increases with increasing Weber number and decreasing pitch. Additionally, the Leidenfrost point was also found to increase with increasing Weber number and decreasing pitch. A scale analysis was performed to explore the effect of resistance to vapor escape through micropost arrays on thermal atomization, and the resulting scaling describes the experimental findings well. (C) 2020 Elsevier Ltd. All rights reserved.