The NPH, a heat-transfer engineer by training, directed me to this article about some surprising qualities of graphene. Most matter follows a well-recognized law requiring that its heat-transfering properties remain constant regardless of its volume. Graphene, in arrogant disregard of this law, gets better at transferring heat the bigger your sample is. I have no idea why; the answer seems to have something to do with the rigid molecular structure, which transmits the heat "signal" without dissipating it very fast, and something to do with what the journalist is pleased to call "reduced dimensionality" (close-packing of molecules?). It's like a reverse case of the "telephone game."
Anyway, apparently it's a big deal for the electrical engineers, who are always on the lookout for tiny bits of things that can do their work without overheating themselves and everyone around them. Many of the amazing gadgets we take for granted these days are possible only because engineers found a way to perform tasks with tiny moving parts that didn't generate more heat than could be quickly and safely dissipated.
The NPH used to spend a lot of time, too, worrying about how hot some things could get in zero-gravity on the Space Station, where the "hot air rises" rule doesn't apply, which means air doesn't circulate the way we take for granted down here: convection cooling doesn't happen without a lot of fans. They say the fan noise got to be quite a problem on the Station, and of course the fan motors contribute to the heat problem themselves. On the Station's exterior, the problem was even more acute. In vacuum, all you get is radiative transfer to dissipate the heat with, which isn't always easy if you're in sunlight or even reflected Earthlight.
1 comment:
This is fascinating. It is interesting enough that it varies at all, because that violates a law long postulated by physics. It does seem to follow a law of its own, though: "the thermal conductivity logarithmically increases as a function of the size of the graphene sample."
It'll be interesting to see what the engineers come up with.
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