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jeudi 3 octobre 2013

When water misbehaves: Amazing video reveals how super-high temperatures cause droplets to travel UPHILL

  • This is because of something known as the 'Leidenfrost Effect'
  • The effect causes the water to levitate on the evaporated gas vapour 
  • Movement can be changed by adjusting the surface texture and temperature

If you’ve ever spilt water on a hot pan, you’ve seen the Leidenfrost Effect in action.

The skittering and fizzing that takes place happens because the surface is super-hot- about twice as hot as the liquid's boiling point.

This causes the water to levitate on the evaporated gas vapour which acts a barrier that keeps the droplet and the hot surface separated.

Scroll down for video...


The skittering of water occurs because a surface is about twice as hot as the liquid's boiling point. This causes the water to levitate on the evaporated gas vapour which acts a barrier that keeps the droplet and the hot surface separated


Bath University’s Alex Grounds and Richard Still looked at how droplets travel on different textured surfaces, heated at varying temperatures.

They found that they could change the direction of the droplets’ movement by changing the temperature of the ratcheted surface.

They also found that droplets can be made to climb up a steep incline – the sharper the teeth of the surface, the steeper incline they were able to climb.

Water droplets make their OWN way through a metal maze




And so the Leidenfrost Maze was created.

The maze guides the water droplets in different directions using specially-arranged grooved hotplates.

‘We think the droplets change direction depending on how fast the gas evaporates from the surface of the droplet and how much the droplet is levitating, combined with the effect of the textured surface that allows it to be propelled along and even go uphill,’ said researcher Alex Grounds.

The research could be used to develop more sophisticated methods for controlling small droplets and heat transfer, such as cooling systems without moving parts.




Researchers at Bath University have found that water droplets can be made to climb up a steep incline using the Leidenfrost effect – the sharper the teeth of the surface, the steeper incline they were able to climb



The Leidenfrost Maze guides water droplets in different directions using specially-arranged grooved hotplates


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THE LEIDENFROST EFFECT
When a liquid hits something really hot - about twice as hot as the liquid's boiling point - it never comes directly in contact with its surface.

This is because vapour acts as a barrier that keeps the two separated. The skittering of water you see when it hits a hot pan is the Leidenfrost effect.


By ELLIE ZOLFAGHARIFARD

PUBLISHED: 17:27 GMT, 3 October 2013 | UPDATED: 19:31 GMT, 3 October 2013

Read more: http://www.dailymail.co.uk/sciencetech/article-2442638/Leidenfrost-Effect-makes-high-temperature-water-travel-uphill.html#ixzz2ggoZ1BKn
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