ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
ENHANCED WATER EVAPORATION WITH FLOATING SYNTHETIC LEAVES
Resumo
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.
Palavras-chave:
Boiling and evaporation, Porous media, Synthetic trees, Negative pressure, Diffusion