摘要
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 Nigraphene surface enables exceptional long-term condensation from days to more than 3 years under practical or even more aggressive testing environments.
冷凝过程广泛存在于发电、海水淡化、天然气分离、空气除湿及水收集等工业应用中.相对于现阶段工业系统应用中传统的膜状冷凝,滴状冷凝可以通过形成分散状可移动的液滴,大大减少冷凝过程中液膜所形成的热阻,从而提供高出一个数量级的传热速率.滴状冷凝因其巨大的传热效率提升而受到广泛的关注和相关研究.在过去,改变冷凝表面润湿性是通用的一种提供滴状冷凝的方法.这种方式使得滴状冷凝及其依赖于非润湿性表面涂层的可靠性及使用寿命.然而高温高湿水蒸气及实际冷凝过程中的温度变化和表面氧化可以快速降低常用疏水涂层的可靠性和使用寿命,使得实际使用过程中的滴状冷凝消失,退变成传统的膜状冷凝.本文提出一种基于多层石墨烯-镍基底的低接触角新型疏水涂层.研究发现,气相沉积方法生长的石墨烯是一种天然的在微纳米尺度混合润湿表面.石墨烯晶界可以增强水滴凝结密度并有效控制水滴生长方向和阻止其合并,从而保持在高热流工况下的滴状冷凝.此涂层被验证在模拟真实甚至更恶劣的工况下可以提供长达3年的持久性滴状冷凝.
作者
Wei Chang
Benli Peng
Karim Egab
Yunya Zhang
Yaqi Cheng
Xiaodong Li
Xuehu Ma
Chen Li
常伟;彭本利;Karim Egab;张云崖;程雅琦;李晓东;马学虎;李琛(Department of Mechanical Engineering,University of South Carolina,SC 29208,USA;Department of Mechanical and Aerospace Engineering,University of Virginia,Charlottesville,VA 22904,USA;State Key Laboratory of Fine Chemicals,Liaoning Provincial Key Laboratory of Clean Utilization of Chemical Resources,Institute of Chemical Engineering,Dalian University of Technology,Dalian 116024,China;Naval Architecture and Ocean Engineering College,Dalian Maritime University,Dalian 116026,China)
基金
supported by the National Science Foundation(NSF)Program of thermal transport processes under Grant No.1336443。
