Su Ching-Yuan, Yang Chien-Yuh, Jhang Bo-Wei, Hsieh Yu-Ling, Sin Yu-Yu, Huang Cheng-Chun
Dep. of Mechanical Engineering, National Central University, Tao-Yuan 32001, Taiwan.
Graduate Institute of Energy Engineering, National Central University, Tao-Yuan 32001, Taiwan.
ACS Appl Mater Interfaces. 2020 Mar 4;12(9):10233-10239. doi: 10.1021/acsami.9b18463. Epub 2020 Feb 19.
Graphene has been applied to thermal technology including boiling and condensation heat transfer, from which the pool boiling enhancement relies on adjusting the surface morphology and wettability that is favorable to catalyze the vaporization on the fluid/graphene interface. However, previous works using graphene or reduced graphene oxide (RGO) flake coatings, where the morphology of graphene coating is nonuniform and most of the underlying structured cavities are sealed by graphene flakes. For a long time, this hampered the unraveling of the mechanism behind the enhanced boiling performance by graphene coatings. Moreover, the previous work relied on using water-based pool boiling, which limits the scope of its practical applications since the versatile nonpolar refrigerant has been widely used in boiling heat transfer. The pool boiling was carried out on a plain copper surface to study the effect of fluorinated graphene (F-graphene) coating using nonpolar refrigerant R-141b as the working fluid along with bubble dynamic visualization. It was found that the increase of contact angle leads to more active cavities and enhances heat transfer performance up to twice as much, by applying the F-graphene coating. Moreover, the mechanism of graphene-enhanced heat transfer performance was unraveled and mainly attributed to the hydrophobic surface and effective cavity structure. This research provides a practical and reliable route for enhancing the heat transfer through F-graphene-coatings, which paves the way for potential application in graphene-based thermal technologies.
石墨烯已应用于包括沸腾和冷凝传热在内的热技术领域，其中池沸腾强化依赖于调整表面形态和润湿性，这有利于催化流体/石墨烯界面上的汽化。然而，以往使用石墨烯或还原氧化石墨烯（RGO）薄片涂层的研究中，石墨烯涂层的形态并不均匀，且大部分底层结构腔被石墨烯薄片密封。长期以来，这阻碍了对石墨烯涂层增强沸腾性能背后机制的揭示。此外，以往的研究依赖于水基池沸腾，由于通用的非极性制冷剂已广泛应用于沸腾传热，这限制了其实际应用范围。在普通铜表面进行池沸腾实验，以研究使用非极性制冷剂R - 141b作为工作流体的氟化石墨烯（F - 石墨烯）涂层的效果，并进行气泡动态可视化研究。研究发现，通过应用F - 石墨烯涂层，接触角的增加会导致更多活性腔，并将传热性能提高两倍之多。此外，揭示了石墨烯增强传热性能的机制，主要归因于疏水表面和有效的腔结构。该研究为通过F - 石墨烯涂层强化传热提供了一条切实可行且可靠的途径，为基于石墨烯的热技术的潜在应用铺平了道路。
