Applications of this could be better solar cells, materials that behave like one-way valves for heat flow and heat-based computing platforms.
The heat flow rate between two objects has a limit that depends on details like the size of the objects, the surfaces that are facing one another, their temperatures, and the distance between them. Heat travels between objects as electromagnetic waves, such as infrared radiation and visible light.
Previously, Reddy and Meyhofer had led a study showing that heat can travel 10,000 times faster than expected between objects separated by nanoscale gaps.
They spent many months in the Lurie Nanofabrication Facility making matched pairs of semiconductor rectangular plates but about a thousand times smaller in length and width. The thickness of the rectangular plates was anywhere between 10,000 nanometers (0.01 millimeters) to 270 nanometers. He suspended these on very narrow beams about a hundred times thinner than human hair.
Heat would ordinarily be expected radiate from each of the six sides in proportion to the surface area. Extremely thin structures about half the wavelength of green light—those edges released and absorbed much more heat than anticipated.
After many hours running the model on a supercomputer, Zhu’s results confirmed that the 100-fold enhancement in heat flow occurs because of the way that waves move in the very thin plates. Since the waves run parallel to the plate’s longer dimensions, the heat shoots out the edges. In the identical plate absorbing the energy, the same concept was at work.
Researchers believe they can control 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). 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.
Research Papers
Hundred-fold enhancement in far-field radiative heat transfer over the blackbody limit
Nature – Hundred-fold enhancement in far-field radiative heat transfer over the blackbody limit
Radiative heat transfer (RHT) has a central role in entropy generation and energy transfer at length scales ranging from nanometers to light years. The blackbody limit, as established in Max Planck’s theory of RHT, provides a convenient metric for quantifying rates of RHT because it represents the maximum possible rate of RHT between macroscopic objects in the far field—that is, at separations greater than Wien’s wavelength. Recent experimental work has verified the feasibility of overcoming the blackbody limit in the near field but heat-transfer rates exceeding the blackbody limit have not previously been demonstrated in the far field. Here we use custom-fabricated calorimetric nanostructures with embedded thermometers to show that RHT between planar membranes with sub-wavelength dimensions can exceed the blackbody limit in the far field by more than two orders of magnitude. The heat-transfer rates that we observe are in good agreement with calculations based on fluctuational electrodynamics. These findings may be directly relevant to various fields, such as energy conversion, atmospheric sciences and astrophysics, in which RHT is important.
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Reading the CoolChips technology section, their tech sounds very interesting, but operating on completely different principals from this stuff. HOWEVER, both effects occur when you have nanometer sized gaps. So investigation of any one effect would have to be very careful to not get confused by the other effect.
Reading the CoolChips technology section their tech sounds very interesting but operating on completely different principals from this stuff.HOWEVER both effects occur when you have nanometer sized gaps. So investigation of any one effect would have to be very careful to not get confused by the other effect.
So here we go again, projecting from 10micro meters^2 to 10 meters^2 houses, just a factor of 1×10^12 based on some preliminary research that obviously cannot economically scale. How about cooling those hot goats in timbuktu?
So here we go again projecting from 10micro meters^2 to 10 meters^2 houses just a factor of 1×10^12 based on some preliminary research that obviously cannot economically scale. How about cooling those hot goats in timbuktu?
Reading the CoolChips technology section, their tech sounds very interesting, but operating on completely different principals from this stuff.
HOWEVER, both effects occur when you have nanometer sized gaps. So investigation of any one effect would have to be very careful to not get confused by the other effect.
So here we go again, projecting from 10micro meters^2 to 10 meters^2 houses, just a factor of 1×10^12 based on some preliminary research that obviously cannot economically scale. How about cooling those hot goats in timbuktu?
Exactly. Once you have this tool in your engineering tool box, I’m sure there are lots of applications. The idea of one way heat transfer valves is interesting too. If you want to pump heat in one direction, having a heat valve would be very useful. A fluctuating magnetic field has much the same effect as fluctuating pressure, it makes material hotter and colder. So apply field → material B gets hotter → heat flows through heat valve to heat sink C, does NOT flow into refrigerated location A turn field off → material B is now colder than starting condition → heat does NOT flow back from heat sink C, but instead flows from refrigerated location A into B. You now have a heat pump that operates on a nanometer scale. Sure you could do it by peltier junctions, but this way doesn’t involve electric currents. One more tool for the designers.
Exactly. Once you have this tool in your engineering tool box I’m sure there are lots of applications.The idea of one way heat transfer valves is interesting too. If you want to pump heat in one direction having a heat valve would be very useful. A fluctuating magnetic field has much the same effect as fluctuating pressure it makes material hotter and colder. So apply field → material B gets hotter → heat flows through heat valve to heat sink C does NOT flow into refrigerated location Aturn field off → material B is now colder than starting condition → heat does NOT flow back from heat sink C but instead flows from refrigerated location A into B.You now have a heat pump that operates on a nanometer scale. Sure you could do it by peltier junctions but this way doesn’t involve electric currents. One more tool for the designers.”
Or moving heat between two differently rotating parts, like a sensor and a radiator, and you want to avoid contact (thus a rotating seal).
Or moving heat between two differently rotating parts like a sensor and a radiator and you want to avoid contact (thus a rotating seal).
If you have a need for non-contact thermal transfer…” Cooling electronics for example.
If you have a need for non-contact thermal transfer…””Cooling electronics for example.”””
It’s basically saying “surprise! weird things happen when objects are closer to each other than the wavelength of IR radiation”, I think. If you have a need for non-contact thermal transfer in a vacuum, this might work, provided you can maintain the subwavelength distance.
It’s basically saying surprise! weird things happen when objects are closer to each other than the wavelength of IR radiation””” I think. If you have a need for non-contact thermal transfer in a vacuum this might work”” provided you can maintain the subwavelength distance.”””
I’m not sure I understand. Is this measuring radiative heat transfer between a emitter and receiver, situated just nanometers apart? If so, that may have some interesting uses, but not quite the revolutionary impact being suggested in the summary. If, however, they are saying that there is 100x increase in emissions from the edges of closely coupled emitter elements, then the potential for a revolution certainly exists. It’s simply dependent on our ability to build micro/nano-meter scale structures quickly and cheaply.
I’m not sure I understand. Is this measuring radiative heat transfer between a emitter and receiver situated just nanometers apart? If so that may have some interesting uses but not quite the revolutionary impact being suggested in the summary. If however they are saying that there is 100x increase in emissions from the edges of closely coupled emitter elements then the potential for a revolution certainly exists. It’s simply dependent on our ability to build micro/nano-meter scale structures quickly and cheaply.
Exactly. Once you have this tool in your engineering tool box, I’m sure there are lots of applications.
The idea of one way heat transfer valves is interesting too. If you want to pump heat in one direction, having a heat valve would be very useful. A fluctuating magnetic field has much the same effect as fluctuating pressure, it makes material hotter and colder.
So apply field → material B gets hotter → heat flows through heat valve to heat sink C, does NOT flow into refrigerated location A
turn field off → material B is now colder than starting condition → heat does NOT flow back from heat sink C, but instead flows from refrigerated location A into B.
You now have a heat pump that operates on a nanometer scale. Sure you could do it by peltier junctions, but this way doesn’t involve electric currents. One more tool for the designers.
Or moving heat between two differently rotating parts, like a sensor and a radiator, and you want to avoid contact (thus a rotating seal).
” If you have a need for non-contact thermal transfer…”
Cooling electronics for example.
It’s basically saying “surprise! weird things happen when objects are closer to each other than the wavelength of IR radiation”, I think. If you have a need for non-contact thermal transfer in a vacuum, this might work, provided you can maintain the subwavelength distance.
I’m not sure I understand. Is this measuring radiative heat transfer between a emitter and receiver, situated just nanometers apart? If so, that may have some interesting uses, but not quite the revolutionary impact being suggested in the summary. If, however, they are saying that there is 100x increase in emissions from the edges of closely coupled emitter elements, then the potential for a revolution certainly exists. It’s simply dependent on our ability to build micro/nano-meter scale structures quickly and cheaply.