09/19/2012
Boiling water without bubbles
A new way of boiling water without creating bubbles could help to reduce the risk of explosions in nuclear reactors and chemical plants.
The technique is based on Leidenfrost effect, which causes water dropped on an extremely hot surface to evaporate and form a vapor layer on which the liquid floats without bubbling. Once the surface layer cools, however, the vapor layer collapses and the water will begin to bubble violently.
To counteract this, it is possible to develop a way to keep the hot water away from the material, allowing the vapor barrier to stay in place as the material cools and prevent explosive bubbling. A rough texture is given to steel balls by covering them with a hydrophobic coating, which causes the water droplets to stretch across the surface grooves and fill the cavities with vapor. This causes the vapor barrier to slowly dissipate as the material cools and allows the surrounding water to remain bubble-free, even as the temperature of the balls drops from over 700° F to 210° F.
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