Japanese scientists say there's a process that could be a focus for making electricity-generating plants more efficient -- and you've seen it every time you've uncorked a bottle of champagne.
That uncorking releases pressure on the liquid, and bubbles form within it. In a process known as Ostwalt ripening -- named for the scientist who discovered it in 1896 -- the more energetic larger bubbles attract molecules from the smaller ones and grow even bigger.
What's that got to do with power plants? Well, bubbles that form in the heated water being converted into steam to drive a plant's electricity-generating turbines can reduce the efficiency of that conversion, researchers have found.
A majority of power stations use boilers for converting the water to steam, but understanding what's happening inside the boiler -- particularly how bubbles form -- has been an elusive goal.
In the superheated setting of a power plant it's been impossible up until now to calculate the rate of bubble formation.
Now researchers from the University of Tokyo, Kyusyu University and private research institute RIKEN, a private research institute in Tokyo, have used a powerful computer network to simulate the formation of bubbles, resulting in a breakthrough in the understanding Oswalt ripening that they've detailed in a study published in the Journal of Chemical Physics.
In such a simulation, virtual molecules are assigned initial velocities and then studied to see how they move, utilizing Newton's law of motion to track their positions over time.
"A huge number of molecules, however, are necessary to simulate bubbles -- on the order of 10,000 are required to express a bubble," researcher Hiroshi Watanabe explained. "So we needed at least this many to investigate hundreds of millions of molecules -- a feat not possible on a single computer."
Using RIKEN's network -- the most powerful in Japan with 4,000 processors -- the researchers simulated an incredible 700 million particles and followed them through a million time steps.
Their key finding is that a classical theory developed in the 1960's to explain how bubbles form in foams, metallic alloys and even freezing ice cream works just as well when it comes to describing gas bubbles in liquids, something that previous experimental efforts had failed to confirm.
An improved understanding of the behavior of such bubbles could enable engineers to design more efficient power stations, the researchers say.
