title: Dropwise Evaporative Cooling of Heated Surfaces with Various Wettability Characteristics Obtained by Nanostructure Modifications.
abstract: A numerical and experimental investigation was conducted to analyze dropwise evaporative cooling of heated surfaces with various wettability characteristics. The surface wettability was tuned by nanostructure modifications. Spray-cooling experiments on these surfaces show that surfaces with better wettability have better heat transfer rate and higher critical heat flux (CHF). Single droplet impingement evaporative cooling of a heated surface was then investigated numerically with various wettability conditions to characterize the effect of contact angle on spray-cooling heat transfer. The volume of fluid (VOF) model with variable-time stepping was used to capture the time-dependent liquid-gas interface motion throughout the computational domain with the kinetic theory model used to predict the evaporation rate at the liquid-gas interface. The numerical results agree with the spray-cooling experiments that dropwise evaporative cooling is much better on surfaces with better wettability because of the better liquid spreading and convection, better liquid-solid contact, and stronger liquid evaporation.
authors.affiliation: Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China.
authors.forename: Jian-Nan
authors.initials: JN
authors.lastname: Chen
authors.affiliation: Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China.
authors.forename: Xiao-Long
authors.initials: XL
authors.lastname: Ouyang
authors.affiliation: Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Beijing Key Laboratory for CO2 Utilization and Reduction Technology, Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China. jiangpx@tsinghua.edu.cn.
authors.forename: Pei-Xue
authors.initials: PX
authors.lastname: Jiang
keywords: Droplet; Evaporation; Spray cooling; Wettability; ZnO nanowires