Effect of Nanostructured Roughness on Evaporating Thin Films in Microchannels for Wenzel and Cassie–Baxter States
Effect of Nanostructured Roughness on Evaporating Thin Films in Microchannels for Wenzel and Cassie–Baxter States
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DOI：
10.1115/1.4023230
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发表时间：
2013-04
影响因子：
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通讯作者：
Jun-jie Zhao;Y. Duan;Xiao-dong Wang;B. Wang
中科院分区：
文献类型：
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作者：
Jun-jie Zhao;Y. Duan;Xiao-dong Wang;B. Wang
基于扩展的Young-Laplace方程和动力学理论，建立了微通道内Wenzel态和Cassie-Baxter态下纳米结构粗糙度对扩展蒸发弯月面的影响模型.粗糙度的几何形状分析相关的分离压力，滑移长度和粗糙层的热阻。结果表明，对于Wenzel态，等效Hamaker常数和吸附膜厚度随纳米柱高度的增加而增加。因此，对于Wenzel状态，蒸发薄膜的铺展和润湿性质随着粗糙度而增加，从而导致与平坦亲水表面相比的细长薄膜和增强的传热速率。对于Cassie-Baxter态，随着纳米柱高度的增加，等效Hamaker常数和分离压力效应减小。对于Cassie-Baxter状态，随着滑移长度的增加和粗糙度的减小，系统的润湿性、薄膜长度和传热速率增加。对于Cassie-Baxter状态，粗糙表面上较小的粗糙度与较大的滑移长度共存，导致相对于平坦表面的高得多的传热速率。
A model based on the augmented Young–Laplace equation and kinetic theory was developed to describe the nanostructured roughness effects on an extended evaporating meniscus in a microchannel for Wenzel and Cassie–Baxter states. The roughness geometries were analytically related to the disjoining pressure, slip length and thermal resistance across the roughness layer. The results show that the equivalent Hamaker constant and adsorbed film thickness increase with nanopillar height for Wenzel state. Thus, the spreading and wetting properties of the evaporating thin film increase with roughness for Wenzel state, leading to an elongated thin film and enhanced heat transfer rate compared to a flat hydrophilic surface. The equivalent Hamaker constant and disjoining pressure effect decrease with increasing nanopillar height for Cassie–Baxter state. The system wettability, thin film length and heat transfer rate increase with increasing slip length and with decreasing roughness for Cassie–Baxter state. A smaller roughness coexisting with a larger slip length on rough surfaces for Cassie–Baxter state results in a much higher heat transfer rate relative to a flat surface.