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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 WATER EVAPORATION WITH FLOATING SYNTHETIC LEAVES

Get access (open in a dialog) DOI: 10.1615/IHTC16.bae.023736
pages 979-989

Аннотация

The evaporation of water exposed to a subsaturated environment is relevant for a variety of water harvesting and energy harvesting applications. Here, we show that the diffusive evaporation rate of water can be greatly modulated by floating a nanoporous synthetic leaf at the water's free interface. The floating leaf was able to evaporate at least as much water as a free interface under equivalent conditions, which is remarkable considering that only about a third of the leaf's interface is open to the ambient. We attribute the enhanced evaporation of the water menisci to their sharp curvature and three-dimensional surface area. At low humidities the water menisci cannot achieve a local equilibrium, due to the mismatch in water activity across the interface outcompeting the negative Laplace pressure. As a result, the mensici retreat partway into the leaf, which increases the local humidity directly above the menisci until equilibrium is reached. Using a ceramic disk with pore diameters of 160 nm, we find the surprising result that leaves exposed to an ambient relative humidity of 95% can evaporate water at the same rate as leaves exposed to only 50% humidity, due to the long and tortuous vapor pathway in the latter case.