|Title||Nanoscale Objects Can Radiate Heat Much Faster Than What Would Normally be Possible|
|Date||Tuesday September 11 2018, @04:20AM|
|from the Nanoscale—so-hot-right-now dept.|
Heat transfer surprise could lead to thermal transistors
As much as 100 times more heat than predicted by the standard radiation theory can flow between two nanoscale objects, even at bigger-than-nanoscale distances, researchers at the University of Michigan and the College of William and Mary have reported in the journal Nature. The new results could have implications for better solar cells, materials that behave like one-way valves for heat flow and perhaps even a heat-based computing platform.
Max Planck's theory of radiation, proposed in 1900, set the stage for quantum mechanics and has held up well over the intervening century. But five years ago, a microstructure in the lab of Pramod Reddy, U-M professor of mechanical engineering, was letting an astonishing amount of heat flow between objects that should have been insulated from one another. [...] In an object the size and shape of a credit card, heat would ordinarily radiate from each of the six sides in proportion to the surface area. But the team found that when the structures were extremely thin—at the thinnest, about half the wavelength of green light—those edges released and absorbed much more heat than anticipated.
[...] While the effect is strongest at the microscale and smaller, the emerging field of nanotechnology could mean that we will see this new idea used in devices. "You could potentially control heat in new ways because we have identified the mechanism of heat transfer," Reddy said.
Examples proposed by the team include controlling the flow of heat in a way similar to how electronics manage electrons, making heat transistors for next-generation computers and diodes (like one-way valves). For example, future building materials could let heat out during cool summer nights but keep it in during the winter. Solar cells could harness the portion of the sun's spectrum that isn't converted to electricity for other purposes. A roof installation could send this lost energy to heat water, for instance. Reddy cautions that a heat-based computing device would be slower and larger than an electronic version, but he believes it might be preferable in certain situations, such as high-temperature environments where conventional electronics are damaged.
Hundred-fold enhancement in far-field radiative heat transfer over the blackbody limit (DOI: 10.1038/s41586-018-0480-9) (DX)
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