Chang Wei, Peng Benli, Egab Karim, Zhang Yunya, Cheng Yaqi, Li Xiaodong, Ma Xuehu, Li Chen
Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA.
Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA; Naval Architecture and Ocean Engineering College, Dalian Maritime University, Dalian 116026, China.
Sci Bull (Beijing). 2021 Sep 30;66(18):1877-1884. doi: 10.1016/j.scib.2021.06.006. Epub 2021 Jun 7.
Condensation is critical for a wide range of applications such as electrical power generation, distillation, natural gas processing, dehumidification and water harvest, and thermal management. Compared with "filmwise" mode of condensation (FWC) prevailing in industrial-scale systems, dropwise condensation (DWC) can provide an order of magnitude higher heat transfer rate owing to drastically reduced thermal resistance from the formation of discrete and mobile droplets. In the past, promoting DWC by controlling surface wetting has attracted wide attention, but DWC highly relies on non-wetting surfaces and only lasts days under practical conditions due to the poor reliability of coatings. Here, we developed nanostructured graphene coatings on nickel (Ni) substrates that we can control and enhance the nucleation of water droplets on graphene grain boundaries. Surprisingly, this enables DWC even under normal "wetting" conditions. This is contradictory to the widely accepted DWC mechanism. Moreover, the Ni-graphene surface enables exceptional long-term condensation from days to more than 3 years under practical or even more aggressive testing environments.
冷凝对于广泛的应用至关重要，如发电、蒸馏、天然气处理、除湿和集水以及热管理。与工业规模系统中普遍存在的“膜状”冷凝模式（FWC）相比，滴状冷凝（DWC）由于离散和移动液滴的形成导致热阻大幅降低，能够提供高一个数量级的传热速率。过去，通过控制表面润湿性来促进滴状冷凝受到了广泛关注，但滴状冷凝高度依赖于非润湿性表面，并且由于涂层可靠性差，在实际条件下只能持续几天。在此，我们在镍（Ni）基底上开发了纳米结构的石墨烯涂层，能够控制并增强石墨烯晶界上水滴的成核。令人惊讶的是，这甚至在正常的“湿润”条件下也能实现滴状冷凝。这与广泛接受的滴状冷凝机制相矛盾。此外，镍 - 石墨烯表面在实际甚至更具挑战性的测试环境下能够实现从数天到超过3年的超长冷凝时间。
