Special surface allows water to boil without producing bubbles
Washington: A team of researchers including one of Indian-origin has engineered a special surface which produces no bubbles when the water is boiled.
Researchers from the Northwestern`s McCormick School of Engineering and Applied Science in US, King Abdullah University of Science and Technology, Saudi Arabia and the University of Melbourne have developed the special surface which could help reduce damage to surfaces, prevent bubbling explosions and may someday be used to enhance heat transfer equipment, reduce drag on ships and lead to anti-frost technologies.
"We manipulated what has been known for a long, long time by using the right kind of texture and chemistry to prevent bubbling during boiling," Neelesh A Patankar, co-author of the study, said.
The research outlined how a specially engineered coated surface can create a stable vapour cushion between the surface and a hot liquid and eliminate the bubbles that are created during boiling.
This phenomenon is based on the Leidenfrost effect.
In 1756, the German scientist Johann Leidenfrost observed that water drops skittered on a sufficiently hot skillet, bouncing across the surface of the skillet on a vapour cushion or film of steam.
The vapour film collapses as the surface falls below the Leidenfrost temperature. When the water droplet hits the surface of the skillet, at 100 degrees Celsius, boiling temperature, it bubbles.
To stabilise a Leidenfrost vapour film and prevent bubbling during boiling, Patankar collaborated with Ivan U Vakarelski of King Abdullah University of Science and Technology, Saudi Arabia.
In their experiments, the stabilisation of the Leidenfrost vapour film was achieved by making the surface of tiny steel spheres very water-repellent.
The spheres were sprayed with a commercially available hydrophobic coating - essentially self-assembled nanoparticles - combined with other water-hating chemicals to achieve the right amount of roughness and water repellency.
At the correct length scale this coating created a surface texture full of tiny peaks and valleys.
When the steel spheres were heated to 400 degrees Celsius and dropped into room temperature water, water vapours formed in the valleys of the textured surface, creating a stable Leidenfrost vapour film that did not collapse once the spheres cooled to the temperature of boiling water.
In the experiments, researchers completely avoided the bubbly phase of boiling.
The discovery was published in the journal Nature.
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