Hydrophobic copper nanowires for enhancing condensation heat transfer

Abstract

Rapid droplet removal by regulating surface topology and wettability has been exploited in nature and it is of great importance for a broad range of technological applications including water desalination and harvesting, power generation, environmental control, and thermal management. Recently there have been tremendous efforts in developing nanostructured surfaces for wettability control and enhancing phase-change heat transfer. However, the tendency of condensed droplets to form as pinned state rather than mobile mode on the nanostructured surfaces is likely to limit the applicability of such functionalized surfaces for condensation heat transfer enhancement. Here, we demonstrate enhanced condensation heat transfer on a nanowired hydrophobic copper surface where molecular permeation of water vapor into the separations between nanowires is greatly decreased, rendering spatial control on droplet nucleation and wetting dynamics. We show experimentally and theoretically that this novel strategy allows to achieve a 100% higher overall heat flux over a broadened surface subcooling range, up to 24K, due to highly efficient droplet jumping compared to the state-of-the-art hydrophobic surfaces. These findings reveal that the droplet behaviors and condensation modes can be regulated by spatially controlling the droplet nucleation events on the nanowired surfaces, which paves the way for the design of nanostructured surfaces for enhanced phase-change heat transfer.