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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

ENHANCED DROPWISE CONDENSATION VIA DROPLET REMOVAL INTO OPPOSING WICKED EVAPORATOR

Get access (open in a dialog) DOI: 10.1615/IHTC16.cod.023742
pages 2259-2266

Résumé

The heat transfer coefficient of dropwise condensation increases as the critical departure size of the droplets decreases. However, passive condensers relying on the gravitational removal of condensate are constrained to a large (millimetric) departure size. Nanostructured superhydrophobic surfaces are able to remove micrometric droplets via coalescence-induced droplet jumping, but are not durable under prolonged exposure to steam. Here, we demonstrate a new mechanism for passively removing dropwise condensate that is both durable and allows for the removal of micrometric droplets. Specifically, we place a wicked evaporator directly opposite the condensing surface, such that droplets bridge the gap and wick back into the evaporator. We used highspeed imaging to characterize the bridging-droplet transfer while varying the wettability of the donor surface, the pore size of the receiving surface, and the droplets volume, viscosity, and surface tension. The transfer of a droplet from one surface to another has previously been studied for two solid substrates, but requires the surfaces to move apart from each other after first contact and a significant volume remains adhered to the donor surface. By using a porous receiving surface, we are able to pull nearly 100% of a droplet away from any partially wetting substrate, without any surface movement required after first contact.We expect that these findings should inform the construction of a bridging-droplet vapor chamber, where the condensation heat transfer can be directly tuned by the gap height determining the critical departure size of dropwise condensate.