Dropwise Condensation on Superhydrophobic Microporous Wick Structures
Dropwise Condensation on Superhydrophobic Microporous Wick Structures
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DOI：
10.1115/1.4038854
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发表时间：
2018-07
影响因子：
--
通讯作者：
S. Hoenig;R. Bonner
中科院分区：
文献类型：
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作者：
S. Hoenig;R. Bonner
先前的研究在滴状冷凝（DWC）粗糙的微织构超疏水表面上已经证明了高的传热增强的证据相比，光滑的疏水表面。在这项研究中，我们实验研究使用微孔烧结铜粉铜基板上涂有硫醇基自组装单层，以实现增强DWC的蒸汽在自定义冷凝室。虽然微织构超疏水表面已经显示出有利的液滴生长动力学，精确的传热测量是欠发达的高热通量。烧结铜粉末直径从4 lm到119 lm被用来研究颗粒尺寸对传热的影响。随着粉末直径的减小，竞争的物理因素导致热性能的改善。在一致的操作条件下，我们实验证明了一个超疏水的4 lm直径的微孔铜粉表面相比，光滑的疏水铜表面的局部冷凝传热系数的23%的改善。对于观察到的最小粉末，这种改善主要归因于接触角滞后的减小，如通过离开液滴尺寸的减小所证明的。有趣的是，在空气中测量的固着水滴的接触角滞后与饱和蒸汽冷凝过程中观察到的离开液滴尺寸相矛盾。很明显，纹理化超疏水表面的特定设计对于在高热通量应用中增强冷凝具有深远的意义。[DOI 10.1115/1.4038854]
Previous research in dropwise condensation (DWC) on rough microtextured superhydrophobic surfaces has demonstrated evidence of high heat transfer enhancement compared to smooth hydrophobic surfaces. In this study, we experimentally investigate the use of microporous sintered copper powder on copper substrates coated with a thiol-based self-assembled monolayer to attain enhanced DWC for steam in a custom condensation chamber. Although microtextured superhydrophobic surfaces have shown advantageous droplet growth dynamics, precise heat transfer measurements are underdeveloped at high heat flux. Sintered copper powder diameters from 4 lm to 119 lm were used to investigate particle size effects on heat transfer. As powder diameter decreased, competing physical factors led to improved thermal performance. At consistent operating conditions, we experimentally demonstrated a 23% improvement in the local condensation heat transfer coefficient for a superhydrophobic 4 lm diameter microporous copper powder surface compared to a smooth hydrophobic copper surface. For the smallest powders observed, this improvement is primarily attributed to the reduction in contact angle hysteresis as evidenced by the decrease in departing droplet size. Interestingly, the contact angle hysteresis of sessile water droplets measured in air is in contradiction with the departing droplet size observations made during condensation of saturated steam. It is evident that the specific design of textured superhydrophobic surfaces has profound implications for enhanced condensation in high heat flux applications. [DOI: 10.1115/1.4038854]