title: Heat Transfer through a Condensate Droplet on Hydrophobic and Nanostructured Superhydrophobic Surfaces.
abstract: Understanding the fundamental mechanisms governing vapor condensation on nonwetting surfaces is crucial to a wide range of energy and water applications. In this paper, we reconcile classical droplet growth modeling barriers by utilizing two-dimensional axisymmetric numerical simulations to study individual droplet heat transfer on nonwetting surfaces (90° < θa < 170°). Incorporation of an appropriate convective boundary condition at the liquid-vapor interface reveals that the majority of heat transfer occurs at the three phase contact line, where the local heat flux can be up to 4 orders of magnitude higher than at the droplet top. Droplet distribution theory is incorporated to show that previous modeling approaches underpredict the overall heat transfer by as much as 300% for dropwise and jumping-droplet condensation. To verify our simulation results, we study condensed water droplet growth using optical and environmental scanning electron microscopy on biphilic samples consisting of hydrophobic and nanostructured superhydrophobic regions, showing excellent agreement with the simulations for both constant base area and constant contact angle growth regimes. Our results demonstrate the importance of resolving local heat transfer effects for the fundamental understanding and high fidelity modeling of phase change heat transfer on nonwetting surfaces.
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Shreyas
authors.initials: S
authors.lastname: Chavan
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.|International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Hyeongyun
authors.initials: H
authors.lastname: Cha
authors.affiliation: International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Daniel
authors.initials: D
authors.lastname: Orejon
authors.affiliation: Heat Transfer Center of Excellence, Johnson Controls , Norman, 73069 Oklahoma, United States.
authors.forename: Kashif
authors.initials: K
authors.lastname: Nawaz
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Nitish
authors.initials: N
authors.lastname: Singla
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Yip Fun
authors.initials: YF
authors.lastname: Yeung
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Deokgeun
authors.initials: D
authors.lastname: Park
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Kang
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Chang
authors.affiliation: International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Takata
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois , Urbana, 61801, United States.|International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Nenad
authors.initials: N
authors.lastname: Miljkovic