title: Enhancing dropwise condensation through bioinspired wettability patterning.
abstract: Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Aritra
authors.initials: A
authors.lastname: Ghosh
authors.forename: Sara
authors.initials: S
authors.lastname: Beaini
authors.forename: Bong June
authors.initials: BJ
authors.lastname: Zhang
authors.forename: Ranjan
authors.initials: R
authors.lastname: Ganguly
authors.forename: Constantine M
authors.initials: CM
authors.lastname: Megaridis
mesh_terms: D032701:Biomimetics / Q000379:methods*; D006358:Hot Temperature; D057446:Hydrodynamics; D014867:Water / Q000737:chemistry; D017155:Wettability
chemical_list: D014867:Water