Droplet Growth Dynamics during Atmospheric Condensation on Nanopillar Surfaces

IF 2.7 3区工程技术 Q2 ENGINEERING, MECHANICAL

Nanoscale and Microscale Thermophysical Engineering Pub Date : 2018-07-31 DOI:10.1080/15567265.2018.1495282

M. R. Haque, C. Qu, E. Kinzel, A. Betz

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引用次数: 7

Abstract

ABSTRACT The Gibbs free energy barrier for heterogeneous nucleation of a condensed droplet on a rough surface changes significantly with changes of humidity content in the condensing environment. The influence of environmental factors (ambient temperature and relative humidity) and substrate characteristics (topology, surface chemistry, and substrate temperature) on atmospheric condensation phenomenon is very important to elucidate the condensed droplet wetting state and condensate harvesting applications. Condensation from the humid air has been reported for plain silicon and fabricated nanopillar surfaces to facilitate condensate harvesting. Droplet growth and size distributions were recorded for 90 min. Spherical droplets condensed on the silicon surfaces and irregular-shaped droplets were observed on the nanopillar surfaces due to the pinning effect of the pillars. The effect of droplet pinning on coalescence events has been described based on the energy balance for the condensed droplets. A mathematical model reveals that certain dimensional combinations (pillar pitch, pillar diameter, and pillar height) of the nanopillar geometry are required to exhibit the pinning mechanism for condensed droplets. Regeneration of droplets was observed at void spaces generated from coalescence events. The growth of individual droplets was tracked over multiple time and length scales, starting from nucleation to get further insight into the direct growth and coalescence mechanisms. Abbreviation: ESEM: Environmental Scanning Electron Microscope; HCP: Hexagonal Closed-Packed; MPL: Microsphere Photolithography; RH: Relative Humidity

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纳米柱表面大气冷凝过程中液滴生长动力学

粗糙表面上冷凝液滴非均匀成核的吉布斯自由能垒随着冷凝环境中湿度含量的变化而显著变化。环境因素（环境温度和相对湿度）和基质特性（拓扑结构、表面化学和基质温度）对大气冷凝现象的影响对于阐明冷凝液滴润湿状态和冷凝液收集应用非常重要。据报道，潮湿空气中的冷凝水用于普通硅和制造的纳米柱表面，以促进冷凝水的收集。在90分钟内记录液滴生长和尺寸分布。由于柱的钉扎效应，在硅表面上观察到球形液滴凝结，在纳米柱表面观察到不规则形状的液滴。基于凝聚液滴的能量平衡，描述了液滴钉扎对聚结事件的影响。数学模型表明，需要纳米柱几何形状的某些尺寸组合（柱间距、柱直径和柱高度）来展示凝聚液滴的钉扎机制。在聚结事件产生的空隙处观察到液滴的再生。从成核开始，在多个时间和长度尺度上跟踪单个液滴的生长，以进一步了解直接生长和聚结机制。缩写：ESEM：环境扫描电子显微镜；HCP：六角封闭包装；MPL：微球光刻；RH：相对湿度

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来源期刊

Nanoscale and Microscale Thermophysical Engineering 工程技术-材料科学：表征与测试

CiteScore

5.90

自引率

2.40%

发文量

审稿时长

3.3 months

期刊介绍： Nanoscale and Microscale Thermophysical Engineering is a journal covering the basic science and engineering of nanoscale and microscale energy and mass transport, conversion, and storage processes. In addition, the journal addresses the uses of these principles for device and system applications in the fields of energy, environment, information, medicine, and transportation. The journal publishes both original research articles and reviews of historical accounts, latest progresses, and future directions in this rapidly advancing field. Papers deal with such topics as: transport and interactions of electrons, phonons, photons, and spins in solids, interfacial energy transport and phase change processes, microscale and nanoscale fluid and mass transport and chemical reaction, molecular-level energy transport, storage, conversion, reaction, and phase transition, near field thermal radiation and plasmonic effects, ultrafast and high spatial resolution measurements, multi length and time scale modeling and computations, processing of nanostructured materials, including composites, micro and nanoscale manufacturing, energy conversion and storage devices and systems, thermal management devices and systems, microfluidic and nanofluidic devices and systems, molecular analysis devices and systems.