Electric-Field-Enhanced Condensation on Superhydrophobic Nanostructured Surfaces
Name
Electric-Field-Enhanced Condensation on Superhydrophobic Nanostructured Surfaces.pdf
Description
Main article, figures, and supplementary information
Size
3.41 MB
Format
Adobe PDF
Checksum (MD5)
60f6ccb7b8591f3e0919122c3d500d74
Author(s)
Miljkovic, Nenad
Enright, Ryan
Wang, Evelyn N.
Preston, Daniel John
Date Issued
November 2013
Journal
ACS Nano
Publisher
American Chemical Society (ACS)
Citation
Miljkovic, Nenad, Daniel J. Preston, Ryan Enright, and Evelyn N. Wang. “Electric-Field-Enhanced Condensation on Superhydrophobic Nanostructured Surfaces.” ACS Nano 7, no. 12 (December 23, 2013): 11043–11054.
Version
Author's final manuscript
Abstract
When condensed droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump due to the conversion of excess surface energy into kinetic energy. This phenomenon has been shown to enhance condensation heat transfer by up to 30% compared to state-of-the-art dropwise condensing surfaces. However, after the droplets jump away from the surface, the existence of the vapor flow toward the condensing surface increases the drag on the jumping droplets, which can lead to complete droplet reversal and return to the surface. This effect limits the possible heat transfer enhancement because larger droplets form upon droplet return to the surface, which impedes heat transfer until they can be either removed by jumping again or finally shedding via gravity. By characterizing individual droplet trajectories during condensation on superhydrophobic nanostructured copper oxide (CuO) surfaces, we show that this vapor flow entrainment dominates droplet motion for droplets smaller than R ≈ 30 μm at moderate heat fluxes (q″ > 2 W/cm2). Subsequently, we demonstrate electric-field-enhanced condensation, whereby an externally applied electric field prevents jumping droplet return. This concept leverages our recent insight that these droplets gain a net positive charge due to charge separation of the electric double layer at the hydrophobic coating. As a result, with scalable superhydrophobic CuO surfaces, we experimentally demonstrated a 50% higher overall condensation heat transfer coefficient compared to that on a jumping-droplet surface with no applied field for low supersaturations (<1.12). This work not only shows significant condensation heat transfer enhancement but also offers avenues for improving the performance of self-cleaning and anti-icing surfaces as well as thermal diodes.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1021/nn404707j
