title: Recurrent filmwise and dropwise condensation on a beetle mimetic surface.
abstract: Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation and efficient droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, these properties have conflicting requirements on the structural roughness and surface chemistry of the condensing surface or condensation modes (e.g., filmwise vs dropwise). Despite intensive efforts over the past few decades, almost all studies have focused on the dropwise condensation enabled by superhydrophobic surfaces. In this work, we report the development of a bioinspired hybrid surface with high wetting contrast that allows for seamless integration of filmwise and dropwise condensation modes. We show that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient. Moreover, we propose an analytical model to optimize the surface morphological features for dramatic heat transfer enhancement.
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Kowloon, Hong Kong.
authors.forename: Youmin
authors.initials: Y
authors.lastname: Hou
authors.forename: Miao
authors.initials: M
authors.lastname: Yu
authors.forename: Xuemei
authors.initials: X
authors.lastname: Chen
authors.forename: Zuankai
authors.initials: Z
authors.lastname: Wang
authors.forename: Shuhuai
authors.initials: S
authors.lastname: Yao
mesh_terms: D000818:Animals; D032701:Biomimetics / Q000379:methods*; D001517:Coleoptera; D006358:Hot Temperature; D036103:Nanotechnology / Q000379:methods*; D014835:Volatilization; D017155:Wettability
keywords: dropwise condensation; filmwise condensation; heat transfer enhancement; heterogeneous wettability; nanostructure