Heat Transfer through a Condensate Droplet on Hydrophobic and Nanostructured Superhydrophobic Surfaces
Heat Transfer through a Condensate Droplet on Hydrophobic and Nanostructured Superhydrophobic Surfaces
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DOI：
10.1021/acs.langmuir.6b01903
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发表时间：
2016-08-09
期刊：
影响因子：
3.9
通讯作者：
Miljkovic, Nenad
中科院分区：
文献类型：
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作者：
Chavan, Shreyas;Cha, Hyeongyun;Miljkovic, Nenad
了解非湿表面上水蒸气冷凝的基本机制对于广泛的能源和水应用是至关重要的。在本文中，我们利用二维轴对称数值模拟来协调经典的液滴生长模型障碍，以研究单个液滴在非湿润表面(90度<；theta(A)<；170度)上的热传递。在气液界面加入适当的对流边界条件，发现大部分换热发生在三相接触线上，局部热流密度可比液滴顶部高出4个数量级。结合液滴分布理论表明，对于液滴状冷凝和跳跃式冷凝，以前的建模方法对整体换热的预测不足300%。为了验证我们的模拟结果，我们用光学和环境扫描电子显微镜研究了由疏水和纳米结构的超疏水区域组成的双亲水样品上凝聚水滴的生长，结果表明在恒碱面积和恒接触角生长区域下都与模拟结果非常一致。我们的结果证明了解决局部换热效应对于基本理解和高保真地模拟非润湿表面上的相变换热的重要性。
Understanding the fundamental mechanisms governing vapor condensation on nonwetting surfaces is crucial to a wide range of energy and water applications. In this paper, we reconcile classical droplet growth modeling barriers by utilizing two-dimensional axisymmetric numerical simulations to study individual droplet heat transfer on nonwetting surfaces (90 degrees < theta(a) < 170 degrees). Incorporation of an appropriate convective boundary condition at the liquid vapor interface reveals that the majority of heat transfer occurs at the three phase contact line, where the local heat flux can be up to 4 orders of magnitude higher than at the droplet top. Droplet distribution theory is incorporated to show that previous modeling approaches underpredict the overall heat transfer by as much as 300% for dropwise and jumping-droplet condensation. To verify our simulation results, we study condensed water droplet growth using optical and environmental scanning electron microscopy on biphilic samples consisting of hydrophobic and nanostructured superhydrophobic regions, showing excellent agreement with the simulations for both constant base area and constant contact angle growth regimes. Our results demonstrate the importance of resolving local heat transfer effects for the fundamental understanding and high fidelity modeling of phase change heat transfer on nonwetting surfaces.