Scientists manage to boil water without bubbles

A new type of nanomaterial exploits the Leidenfrost effect, in which droplets of water can skate across hot a hot surface without boiling away, to boil water without creating explosive bubbles. 

|
Dr. Ivan Vakarelski
A tiny, heated steel sphere covered in the new coating, so as it cools there is a continuous film of vapor without bubbling. Without the coating (right) the cooling of the heated rod leads to conventional bubbly boiling.

A new nanomaterial vanquishes the bubbles that normally pop up with boiling, a finding that may point to ways to help prevent explosions in nuclear power plants, researchers say.

To understand how this material works, imagine a hot skillet. When its surface is warm, water on it will bubble. However, once the skillet gets hot enough, the water drops will skitter across its surface as they levitate on a cushion of vapor, an effect known as the Leidenfrost regime after the scientist who investigated it in 1756.

"The Leidenfrost state of a water drop is often used worldwide to gauge the temperature of a hot skillet while cooking," researcher Neelesh Patankar, a mechanical engineer at Northwestern University in Evanston, Ill., told LiveScience.

Tinkering with a surface's properties can alter the temperature at which water touching it goes from this explosive bubbling phase to the Leidenfrost regime. Making a surface hydrophobic, or water-repellant, affects how well heat gets transferred from that surface to water. Making it craggy instead of smooth also controls how heat flows from it. [Top 10 Greatest Explosions]

Scientists developed a craggy super-water-repellant coating made of nanoparticles covered with an organic, hydrophobic compound. (Nanoparticles are particles only nanometers, or billionths of a meter, in size.)

When a steel rod covered with this coating was heated, the result was a continuous film of vapor on the rod without bubbling. "One can make surfaces on which a liquid will never bubble as it starts boiling, a phenomenon that is contrary to the experience of anyone who has ever cooked," researcher Ivan Vakarelski, a physicist at King Abdullah University of Science and Technology in Saudi Arabia, told LiveScience. [See Video of the No-Bubble Boil]

Suppressing the bubbling could help reduce the damage such fizzing has on surfaces. It might also prevent vapor buildup that can lead to explosions, which can be disastrous in the case of nuclear power plants — witness the infamous 1986 Chernobyl disaster in the former Soviet Union, the worst nuclear accident in history.

"In nuclear power plant accidents, powerful vapor explosions can occur when melted fuel is in contact with the coolant liquid," Vakarelski said. When that happens, a vapor film of the coolant liquid is formed next to the molten fuel. As the material cools, the vapor film enters a "bubbly boiling regime," Vakarelski said. "This leads to vapor explosions. It is suggested that such an explosion destroyed the reactor in the case of the Chernobyl accident.

"Our work does show how to stop a vapor film from collapsing to a bubbly boiling phase," Vakarelski said. "As such, the phenomenon we report is the same as that in vapor explosions in nuclear power plants."

However, it seems unlikely that this particular coating will improve nuclear safety, researchers cautioned.

"First, we need a surface with the right kind of texture to eliminate vapor film collapse — it is unclear how this can be done on a molten metal, the fuel," Patankar said. "Second, even if self-assembling nanoparticulates are injected with the coolant to reside on the surface of the molten metal — we don't even know if this can be done — the nuclear reactors operate at much higher temperatures, much beyond the operating conditions of the coating used in our study."

Instead, the researchers suggest future work along similar lines might control how matter behaves in other ways, such as reducing drag on surfaces, preventing the formation of frost or ice, and efficiently transferring heat via boiling and condensation.

The scientists detailed their findings online today (Sept. 12) in the journal Nature.

Copyright 2012 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Scientists manage to boil water without bubbles
Read this article in
https://www.csmonitor.com/Science/2012/0914/Scientists-manage-to-boil-water-without-bubbles
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe