Key design and operating parameters for enhancing dropwise condensation through wettability patterning

Condensation of vapor on metal surfaces has many engineering applications. We demonstrate a facile and scalable approach for accelerated removal of condensate on a vertical plate during condensation of water vapor in the presence of non-condensable gases. We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) laid strategically on a mirror-finish (hydrophilic) aluminum surface that promotes dropwise condensation (DWC). The design facilitates capillary-driven condensate drainage and enhanced DWC heat transfer by reducing the departing droplet size on the DWC regions. The study offers quantitative insight on the promoting and retarding influences of the dropwise and filmwise condensation zones and their ramifications on overall heat transfer on this substrate. An optimal design has been achieved by changing the fractional area of superhydrophilic tracks with respect to the overall condenser plate surface, and optimizing rapid drainage by altering the track spatial layout. The study indicates that heat transfer improvements in excess of 30% can be achieved in this metal system even in the presence of non-condensable gases that are well known to hinder energy transport. (C) 2015 Elsevier Ltd. All rights reserved.