Manipulating Heat Like Light 82
An anonymous reader writes "A new technique allows allows 'thermocrystals' to be created that can manipulate heat (a vibration of the atomic lattice of a material). Predicted manipulations include the ability to selectively transmit, reflect or concentrate heat much like light waves can be manipulated by lenses and mirrors. 'Heat differs from sound, he explains, in the frequency of its vibrations: Sound waves consist of lower frequencies (up to the kilohertz range, or thousands of vibrations per second), while heat arises from higher frequencies (in the terahertz range, or trillions of vibrations per second).' Applications range from better thermoelectric devices to switchable heat insulating/transmitting materials (abstract). Perhaps this will result in better cooling/heating mechanisms or more efficient engines."
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http://science.slashdot.org/story/13/01/05/225256/what-negative-temperature-really-means [slashdot.org]
Yes
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That's what I read into the distinction as well. Of course, they could have just said "thermal phonons".
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So thinks he's a rocket scientist, explain how space with no atomic lattice can radiate heat at a temperature of 2.7K?
Could they redirect only a certain hotness? (Score:5, Interesting)
Maxwell's Demon?
Re:Could they redirect only a certain hotness? (Score:5, Informative)
No.
They first have to select specific wavelengths and then--it sounds like--frequency-shift them.
To call this "heat" is a deliberately misleading statement designed to elicit precisely the question you are asking, as that will attract much more of our most limited resource--attention--to this otherwise interesting but essentially esoteric work.
"Heat" in ordinary parlance is constituted by vibrational modes that obey the principle of equipartition, which this "heat" manifestly does not.
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So essentially it's now ok to overload semantics in scientific writings ?!
I just invented* a safe** and practical*** form of cold-fusion****.
* stole
** for non sentient life forms outside of solar system
*** for the purpose of filling my bank account
**** relative to the sun, not so much to the atmosphere...
This is precisely why C++ sucks Afro-Caucasian***** balls.
***** chocolate milk ice cream.
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I'll grant that this isn't breaking news for most people, but as science reporting goes this is pretty good. It's better than another fad diet or fish oil bullshit story.
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And the energy they refer as light is just the energy "in flight" in "the field" - there's also the energy in the Motion of the matter which is hot (ie, sound). This last can have many different ways of expression beyond just "frequency". These different ways are different degrees of freedom, and once heat energy density is high enough, it always finds a way to create more. For example, adding more atoms to a molecule increases the number of unique modes with which it can shake about... so heat capacity (energy per temperature change) generally depends on molecular complexity. The material with the lowest heat capacity is also the simplest.
Ummm... what? Heat capacity per what? If it's "per mass" - no, it isn't (hydrogen - 14.30 J/g/K, helium- 5.1932, paraffin wax - C25H52 - 2.5 J/g/k). If it is "per mol" - then it's true that more complex molecules will store more thermal energy in the "vibrational degrees of freedom".
This work is fairly ground-breaking because it shows manipulation heat energy in a way we've not known before. Thermal diodes imply possibly more efficient ways of "switching" the flow of heat - and this means more efficient heat pumps / heat exchangers.
The relevant word (missing from your statement above) is "some" - as in "some heat energy" or "the flow of some heat". And is relevant because there's a bit of way until the second law of thermodynamics is "repealed" (the one th
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Napolean already gave Fourier the patent on that.
But this version is transformative! And Faster!
Low-heat electricity generation (Score:3)
I wonder if you could use this to concentrate low levels of heat and generate electricity from it. Not only would you be able to get energy out of (almost) nothing, (albeit, probably not much), but you could cool an area without producing a lot of waste heat.
Re:Low-heat electricity generation (Score:4, Informative)
No, because it would violate the 2nd law of thermodynamics.
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No, because it would violate the 2nd law of thermodynamics.
Does the 2nd law of thermodynamics not apply to a steam generator?
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Concentrating heat and then using it to do work violates the second law of thermodynamics.
If you can concentrate heat, it must be in a setup that would makes a thermal machine not work.
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You can concentrate heat and use it to run a thermal machine. However it will require more work to concentrate the heat than you will get out of the thermal machine.
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We are at about 90% efficiency for them, so not really.
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Yes, in that a steam generator is able to capture energy from the transfer of heat from a hot area to cold area and uses it to do work.
Thermodynamics (Score:2)
It's only a "law" because we do not yet know how to break it.
I, for one, look forward to the day (year, century...) when we decide that it's an obsolete principle. Until we actually know all the rules of the game, all the interactions, all the api of the universe... we cannot know that anything is truly a "law of physics". We can speculate, postulate, investigate, narrow-in-on, or disprove, but never really affirm.
(Which is not to say that this specific mechanism shows any promise, just that some mechanis
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You can imagine a setup with a black body radiator and a theoretical lense and attempt to focus the black body radiation to heat another object to a higher temperature than the original black body. And it is not possible. The laws of thermodynamics apply of course but they don't explain the why. If you go through the motions and try to calculate how hot you can get the second object you find you can't get it hot enough. You can't focus the radiation to make it hotter.
Fusion! A/C, Sterling (Score:5, Interesting)
Thermal Diodes: Hook this to a solar collecting sterling engine for a considerable performance boost.
That sounds like passive Heating & Air conditioning. Maybe society will use technology to reduce its power consumption overall.
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my first thought was a "heat laser". the perfect solution to heat dissipation in space....turn it into a weapon!
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Or even spaceships, heat dissipation can be a major issue with long term presences in space.
Not really "heat" (Score:1)
A specific specially created heat (Score:5, Informative)
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I presume we are then talking about phonon manipulation. Which is pretty cool (sorry for that pun) but at the moment I can't see a lot of applications. Should be able to do lots of interesting photon like things but much slower. Useful if you want to embed logic in a solid material.
Heat diodes (Score:3)
From TFA:
The crystals could also be used to create thermal diodes: materials in which heat can pass in one direction, but not in the reverse direction. Such a one-way heat flow could be useful in energy-efficient buildings in hot and cold climates.
Other variations of the material could be used to focus heat — much like focusing light with a lens — to concentrate it in a small area. Another intriguing possibility is thermal cloaking,
Some of the speculative uses seem pretty interesting. To date it is only 40% efficient at some of these tasks, but that's not bad for starters.
These things sound like beginnings of heat circuitry components. The method involves making alloys of silicon that incorporate nanoparticles of germanium in a particular size range, and layering these thin films. If they can find a dynamically controllable switch structure you could build most of the necessary components for simple circuits.
Then you run into this sentences from TFA:
Heat also spans a wide range of frequencies, he says, while sound spans a single frequency.
Wow. Journalism student I'm guessing?
Wha? (Score:2)
Sound is pressure waves. Heat, or more accurately, infrared, is electromagnetic radiation.
They are so vastly different, far beyond just frequency, that I'm not sure what the person who wrote the summary is smoking. :)
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A swing and a miss... While things with temperature will emit blackbody radiation, which corresponds with IR for temperatures humans typically deal with in day to day stuff, and it is possible for a photon gas to have a temperature and distribution, neither of those make heat synonymous with IR or light in general. E&M radiation covers transfer by irradiation, but convection and conduction are handled by vibrations and motion of particles.
Heat and Light (Score:2)
Face Palm!
Heat is vibrating atoms. (Or slightly more accurately, banging off each other randomly like billiard balls.) Some of that energy gets converted and emitted as radiation, and radiation can be absorbed and converted to heat, but that does NOT make them the same thing.
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You need to take your thermodynamic classes again.
Heat and infrared radiation are two very different things.
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Microchips! (Score:1)
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Blackbody radiation isn't from exciting electrons and seeing them decay back to ground-state. That would make blackbody radiation far from smooth and continuous. Instead it is due to the acceleration of charged particles which causes them to emit electromagnetic radiation, which works even with plasma or a soup of pure electrons. It also allows blackbody radiation to go to energies much higher or much lower than what you can find atomic transitions for.
That said, IR can be a component of heat, as can any
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Technically, neither are phonons "heat". Heat is energy in transit, and semantically is not strictly equivalent to any of the mechanisms or consequences of that transfer. However outside of a scientific treatment, this stricture is dropped.
OP is of course incorrect in assume that IR is the only mechanism by which heat can occur.
parent is wrong. period. (Score:1)
Parent is wrong.
I failed High School Physics Day (Score:2)
So I didn't read the article... (Score:2)
misleading blurb or bad paper? (Score:2)
Usually the main problem with press release science is that it has nothing to do with the real science behind it. Probably, there's an MIT professor embarrassed to show up to colloquia right now.
This press release is talking about acoustic metamaterials. The scientific description in the press release is bad, very bad, but one thing they got dead wrong is that this is not new.
A long time issue (Score:1)