Slashdot Mirror
Manipulating Heat Like Light
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."
Maxwell's Demon?
http://science.slashdot.org/story/13/01/05/225256/what-negative-temperature-really-means
Yes
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.
How did this one get missed? Fusion's biggest problem is heat management.
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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These crystals aren't heat sinks. The MIT lab is creating a "heat" that is actually just really fast sound. This can then be manipulated with their special thermocrystals. Now, if they can create a way to turn normal waste heat into this "fast sound" heat, we'll open up a wealth of practical applications.
Occasionally living proof of the Ballmer peak.
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?
Sig Battery depleted. Reverting to safe mode.
You need to take your thermodynamic classes again.
Heat and infrared radiation are two very different things.
Rethinking email
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.
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 part of the spectrum depending on the temperatures dealing with, as heat is the energy transferred between bodies. In some cases that is done by irradiation, other times it is done by conduction which would be driven by vibration and motion of atoms. Internal energy of most thermal systems, on the other hand, is pretty much all vibration or motion though.
That's what I read into the distinction as well. Of course, they could have just said "thermal phonons".
Someone had to do it.