Guo L, Tang G H
MOE Key Laboratory of Thermo-Fluid Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University Xi'an 710049 P. R. China
RSC Adv. 2018 Nov 26;8(69):39341-39351. doi: 10.1039/c8ra08190e. eCollection 2018 Nov 23.
To promote the water vapor condensation efficiency in the presence of a non-condensable gas, both high nucleation rate and efficient droplet departure are desired on the condensing surface. Superhydrophobic surfaces with large water contact angles ensure the dropwise condensation mode and efficient droplet departure ability. Alternatively, efficient nucleation requires the surface to be hydrophilic. To combine these two seemingly contradictory factors on a single surface, we presented a copper-based hydrophilic-slippery surface in this study by depositing a lubricant (trimethoxysilane) on the microstructured copper substrate. The water droplet had both low contact angles and sliding angles on the surface, and stable dropwise condensation could be realized with and without non-condensable gas. The present hydrophilic-slippery surface demonstrated promising potential to enhance condensation heat transfer, particularly for cases with non-condensable gas. Improved droplet mobility was observed as compared to a superhydrophobic surface, hydrophobic surface, and hydrophobic-slippery surface. The most attractive feature lies in the enhanced nucleation process due to hydrophilicity, which is more favorable as it requires small subcooling degree and large non-condensable gas content. By revealing that a sliding angle could be accompanied by a small contact angle, this hydrophilic-slippery surface could improve our understanding in designing new functional surfaces for phase change, anti-icing, self-cleaning, and anti-fouling applications.
为了在存在不凝性气体的情况下提高水蒸气的冷凝效率，冷凝表面既需要高成核速率又需要高效的液滴脱离。具有大水滴接触角的超疏水表面可确保滴状冷凝模式和高效的液滴脱离能力。然而，高效成核需要表面具有亲水性。为了在单个表面上结合这两个看似矛盾的因素，我们在本研究中通过在微结构铜基板上沉积润滑剂（三甲氧基硅烷）制备了一种铜基亲水性光滑表面。水滴在该表面上具有低接触角和滑动角，无论有无不凝性气体都能实现稳定的滴状冷凝。目前的亲水性光滑表面在增强冷凝传热方面显示出有前景的潜力，特别是对于存在不凝性气体的情况。与超疏水表面、疏水表面和疏水光滑表面相比，观察到液滴迁移率有所提高。最吸引人的特征在于由于亲水性而增强的成核过程，这更有利，因为它需要较小的过冷度和较大的不凝性气体含量。通过揭示滑动角可以伴随着小接触角，这种亲水性光滑表面可以增进我们对设计用于相变、防冰、自清洁和防污应用的新型功能表面的理解。
