Best material to retain heat- IR heat
Best material to retain heat- IR heat
(OP)
I am an electrical guy and hope someone can tell me or point me to some discussions on the best materials that are able to not only absorb IR heat but also the best at retaining this heat. Think solar IR waves here. Thanks in advance.





RE: Best material to retain heat- IR heat
Are you looking for a metal?
What product form (tube, plate or ?)
Large solar collectors use tubes of Cu, Al or stainless steel with black coatings. Surface conversion coatings, or even oxides, work better than paints or applied coatings.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Best material to retain heat- IR heat
E.g., a high absorbance surface will radiate quite nicely as well. The only plus side is that you might possibly be able to tailor the surface to be low emissivity in the LWIR regime to minimize radiative loss.
Again, depending on complexity, you may need to reconfigure your outer surface depending on the time of day, i.e., absorbing during the day and reflective at night.
TTFN
RE: Best material to retain heat- IR heat
RE: Best material to retain heat- IR heat
Forgive me but I do not want to divulge all the info as this might be against a non-disclosure agreement my friend has with a company. I am not doing the design just interested in what they are trying to achieve.
Let me ask another question if I may:
As I understand it, if you had two identical pieces of material (dimensions and construction) and you painted one black and one white, the black one would abosrb more heat than the white one but at the same time cool faster than the white one if the heat source is removed. I believe this is basically what IRstuff was referring too.
I believe for what we are trying to achieve, that if what I said is true, the black material would definately be best for absorbing the heat but not sure if we want the heat to radiate away quickly. Is there a color that might sacrifice some absorbtion for better ability to retain the heat (grey)? (Heat transfer is a huge deal as well). If you guys have any links to educate me that would be great too.
The ideal material would be inexpensive (of course) so no elaborate materials would be good. I like the idea of using copper or aluminum. I believe a plate shape would be best for this application.
Thanks to all. I will do some research on the net this weekend and probably have more questions.
RE: Best material to retain heat- IR heat
If you arbitrarily pick 3um as the cut-off, ~80% of the solar energy is below 3um, while >99% of the room temperature radiation is above 3um
TTFN
RE: Best material to retain heat- IR heat
There are two I can think of straight away: spectacle lens that go from clear to dark in a few seconds and battery-operated welder's lens that go from clear to dark in a mili-second. Make two panels so air-space reduces the overall loss of convected heat from retained radiated heat.
RE: Best material to retain heat- IR heat
Would some of the light be reflected if I use black glass? Seems some of it would, or at least more than I would like.
RE: Best material to retain heat- IR heat
TTFN
RE: Best material to retain heat- IR heat
RE: Best material to retain heat- IR heat
The point is when the radiation source is "on" eg daytime black absorbs heat energy relatively faster than any other colour. Conversely, when the radiation source is "off" black will also radiate retained heat energy faster than any other colour. The "logic" if that's what it is, is to devise a strategy to change the black colour to something that reduces radiation loss. Black to clear may be beneficial and the technology to do it is commercially available. Another option is to have something like venetian blinds that are white or silver on one side and black on the other.
RE: Best material to retain heat- IR heat
The plexiglass will allow sunlight in, but will not transmit the radiated LWIR. If the inside box surface is blackened, that'll maximize the sunlight absorption.
This should work like the spectrally selective absorption that I was talking about earlier
TTFN
RE: Best material to retain heat- IR heat
I like your final suggestion IR, I was thinking of a 'building' on your other post. Also like the tinted glass idea.
RE: Best material to retain heat- IR heat
Still looking.
http://www.tiodize.com/emissivity.html