Droplet pattern and condensation gradient around a humidity sink
Résumé
We describe the evolution of a water drop saturated with NaCl and the growth of pure water droplets in a
breath figure pattern (BF) condensing around it. This salty drop acts as a humidity sink, inhibiting the BF inside a
ring at a distance r = δ from the sink center and slowing down BF growth outside the ring. The initial salty drop
is taken either from a salt-saturated solution (type I experiment) or by placing an NaCl crystal on the substrate
(type II experiment). The results are similar, provided that the initial time for type II evolution is taken at the
end of the crystal dissolution. The evolution of the salty drop radius R is deduced from the establishment of a
three-dimensional hyperbolic concentration profile around the salty drop. This profile scales with r/δ. Accounting
for the salt concentration decrease with salty drop growth, R is seen to grow as t 5. In the region r>δ, water
droplets nucleate and grow. The rate of evolution of the water droplets at constant r/δ can be used to determine
the local water pressure. The corresponding data reasonably agree with a hyperbolic water vapor profile around
the salty drop. These results can be applied to the growth of BF patterns to determine whether hyperbolic or
linear water vapor profiles apply
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PhysRevE-C with Erratum.pdf (1.35 Mo)
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ErratumPhysRevE.101.039901.pdf (112.47 Ko)
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