Experimental Investigation of Condensation and Freezing Phenomenon on Hydrophilic and Hydrophobic Titanium Nanopillared Glass Surfaces
Experimental Investigation of Condensation and Freezing Phenomenon on Hydrophilic and Hydrophobic Titanium Nanopillared Glass Surfaces
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DOI：
10.1080/01457632.2019.1707401
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发表时间：
2020-01
影响因子：
2.3
通讯作者：
Mohammad Rejaul Haque;Chen Zhu;C. Qu;E. Kinzel;Amy Rachel Betz
中科院分区：
文献类型：
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作者：
Mohammad Rejaul Haque;Chen Zhu;C. Qu;E. Kinzel;Amy Rachel Betz
摘要大气冷凝在传热、热管理、航空航天、冷凝液收集等诸多实际应用中具有重要意义。当温度低于露点温度时，水滴在表面上不均匀地成核。冷凝液滴的成核能垒随操作环境中的湿度含量而显著变化。这种冷凝物的冻结也取决于操作条件和表面性质。本文介绍了一个实验研究的冷凝和冻结从潮湿的空气，了解如何的表面形态和化学决定的液滴形状和润湿状态的目标。使用微球光刻（MPL）图案化钛（Ti）柱的半平面密堆积阵列。测试具有和不具有Teflon ®涂层的Ti纳米结构表面，以分别揭示冷凝物收集、被动冷冻和滴状冷凝应用。冷凝和冻结测试进行了在不凝性气体（空气）的存在下，具有不同的相对湿度（RH）水平，以控制成核位点密度。实验表明，液滴生长发生在以下几个阶段：初始成核，直接增长，并合并事件。通过钉扎液滴，聚结被抑制的Ti纳米柱表面改变液滴的尺寸分布，并显着加速冻结过程。
Abstract Atmospheric condensation is very important for multiple practical applications such as heat transfer, thermal management, aerospace, and condensate harvesting. Water droplets heterogeneously nucleate on the surfaces when the temperature is below the dew point temperature. The nucleation energy barrier for a condensed droplet varies significantly with the humidity content in the operating environment. The freezing of this condensate is also dependent on the operating conditions and surface properties. This article presents an experimental study of condensation and freezing from humid air with the objective of understanding how the surface morphology and chemistry determines the droplet shape and wetting state. Hexagonal close-packed arrays of titanium (Ti) pillars are patterned using microsphere photolithography (MPL). The Ti nanostructured surface was tested with and without a Teflon© coating to reveal the condensate harvesting, passive freezing, and dropwise condensation applications, respectively. Condensation and freezing tests were conducted in the presence of non-condensable gases (air) with different relative humidity (RH) levels to control the nucleation site density. The experiments showed that droplet growth occurs in the following stages: initial nucleation, direct growth, and coalescence events. By pinning droplets, coalescence is suppressed for the Ti nanopillared surface altering the size distribution of droplets and significantly accelerating the freezing process.