Library Subscription: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Condensation Heat Transfer Characteristics on A Micro-structured Surface With Wettability Gradient

Get access (open in a dialog) DOI: 10.1615/IHTC15.cds.009033
pages 725-736

Abstract

Recently, microscale and nanoscale phase change phenomena have attracted increased research interest following the advancements in MEMS technology for the development of microscale thermal management systems. In terms of condensation heat transfer, dropwise condensation on a hydrophobic surface has better heat transfer performance than filmwise condensation. In ordinary systems, larger droplets tend to depart from the condensing surface due to the effect of gravity or the shear force of vapor flow, resulting in the creation of a bare surface for rapid condensation. However, these forces do not impact microscale and nanoscale systems, primarily due to the limited space available for liquid and vapor flow; this suggests the need for the development of a new method to effectively remove grown droplets from the condensing surface in order to obtain a larger condensation heat transfer rate. To this end, we have performed the challenging task of fabricating microstructures with wettability gradient on the condensing surface, aiming to improve drainage ability. The wettability gradient was formed by gradually changing the pattern width of the hydrophilic surface. Further, we have experimentally verified the effect of wettability gradient on the condensation heat transfer rate. The microstructured condensing surface with wettability gradient was found to display improved drainage efficacy, which can be attributed to the decrease in the flooding area compared with surfaces without wettability gradient.