Slashdot Mirror
Quiet Cooling With a Copper Foam Heatsink
Zothecula writes: The Silent Power PC is claimed to be the first high-end PC able to ditch noisy electric fans in favor of fully passive cooling. In place of a conventional fan, the unit uses an open-air metal foam heatsink that boasts an enormous surface area thanks to the open-weave copper filaments of which it's composed. The Silent Power creators claim that the circulation of air through the foam is so efficient in dissipating heat that the exterior surface temperature never rises above 50 C (122 F) in normal use.
And you can keep the pots and pans clean!
... for a dust free room!
This factor of 500 is a strange number. The copper fins of my CPU-heatsink also have a quite a large total area. A claim of two orders of magnitude needs a bit more justification than just a mention. Otherwise is just seems like a movie title.
This is not a real product. It's just being crowdfunded. The only evidence that it works is a claim by the creators that "the exterior surface temperature never rises above 50 C (122 F) in normal use", without specifying what "normal use" is.
It might work and if so, great! I can't trust this article at this moment, however.
Bought a no-moving-parts power supply back in... oh, I don't know, 2003 or something. Sold as "cooled by heatpipes", pretty much the same principle - silent, no moving parts, passively cooled, no fans, huge surface areas.
They also did kits for the processor itself but I've also bought P2-era motherboards that were designed to be passively cooled too (same thing, huge heatsink, no fan).
So this is certainly not "the first" in the PC world (unless we're talking about "the first" to use some particular technology that just about replicates what I bought over 10 years ago). Not even close. In fact, it's over a decade out. And going outside the PC world, passively cooled chips are pretty common - you have a tablet or smartphone without a huge stonking fan, no?
The PSU is still working 10 years on if you'd like me to dig it out. I'm sure it wouldn't take much to butcher it to do the same job to the processor, especially if you can safely have it clock itself down to prevent heat being generated in the first place.
Assuming the copper filaments are cylindrical in shape, that's a surface area to volume ratio of (2pi*r*l) / (pi*r^2*l) = 2/r.
OTOH, in a copper fin configuration, the ratio of surface area to volume is (2lw) / (lwt) = 2/t.
In other words, if you use the same volume of copper and the thickness of the fin is half the diameter of the sponge cylinders, you have the exact same surface area. The thinner fins may be weaker, but since the additional fin material on the sides reinforces the structural strength, I assume that's not too big a deal. Just place thicker (stronger) fins along the outsides and you have a structure which is much more solid than the sponge.
Now consider that in passive cooling the airflow is slow enough to be laminar. The flat surface of the fins (oriented vertically) will then impose less aerodynamic resistance, leading to higher flowrate, and thus greater heat exchange.
Unless there's something else going on here (maybe the sponge filaments are wrinkled instead of smooth), or it's that much harder to make thin fins than spongy cylinders, I don't see how this could be better than a traditional fin-type heatsink.
"the foam is so efficient in dissipating heat that the exterior surface temperature never rises above 50 C (122 F) in normal use."
Hey, I can glue a chunk of styrofoam on a CPU, and the outside of it won't even get that hot. I wouldn't use that fact to claim that styrofoam makes a great heatsink, though. Quite the opposite.
"National Security is the chief cause of national insecurity." - Celine's First Law
A computer case that doubles as the heat-sink FTW!
http://www.quietpc.com/tnn500a...
Life is not for the lazy.
It's using a Core i7-4785T, an "ultra-low power" processor (shown by the T suffix - S indicates a "low-power" part, and K indicating an overclockable part). This particular one is a 35W part running at only 2.2GHz, while the regular i7-4790 runs at 3.6GHz (and 84W)[citation]. Turbo boost can bring that up to 3.2GHz on a single core (on the regular chip, 4.0GHz). So the CPU is not a regular desktop chip at all, let alone a "high-end" one.
The Nvidia GeForce 760 is a bit of an interesting choice. It's not powerful enough to be called "high-end" (I would apply that label only to the 780 and 780 Ti of that series), but it doesn't fit with the ultra-low power CPU. If they were thermally constrained (as their CPU choice indicates), I would have expected to see the 750 Ti - not too much weaker (~30% [citation]), but with a far lower power draw (it's the most powerful card to be powered only by PCIe, no extra power connections needed). Seriously, the 760 is a 170W card, and the 750 Ti is a 60W card. Seeing how they handicapped the CPU to shave off 50W, I don't see their logic for not shaving 110W for a similar performance penalty.
Because of their choice of CPU, I can't really support their claim of being a high-end desktop with passive cooling. They are much more powerful than most fanless PCs, but most fanless PCs are also designed for industrial use, not for regular office/home environment. So it's an improvement, but not a revolutionary one.
The tiles on the shuttle's belly were the complete opposite. The main tiles on the belly of the shuttle were roughly 10% silica fibers, 90% air. Think very low density styrofoam, except that it can be heated to glowing temperatures without losing its properties. This was actually the really cool demo that I saw. The person giving the demo heated it with a torch until it was glowing yellow/white, then picked it up with his bare finger tips. Because the thermal conductivity of it was so low, it could be handled (with care) with bare hands.
For the OP, the point of the thermal protection system was precisely the opposite of being a heat sink. It's entire purpose was to insulate the shuttle against the heat that the belly was exposed to during re-entry. Contrary to popular belief, the majority of heating during re-entry was due to compressive heat (think diesel engines, boyles law and all that), Not friction. Basically the shuttle would compress the air in front of it, causing it to heat up to plasma type temperatures, which was then transferred to the body of the shuttle through convective heating. As such, the best way to deal with it was just to insulate yourself, and wait for the high temperatures to pass.
...si hoc legere nimium eruditionis habes...
I'm sure the engineers have taken care of that problem. As a matter of fact, I'm just testing the product and...oh shit, my shirt is on fire...
With finned heat sinks, one of the limits on size was that the comparatively low conductivity of the fin material made surface area increasingly unhelpful as you got further from the heat source. Especially with paper-thin lightweight aluminum you could just keep making them bigger; but much of the fin would be essentially wasted because the delta-T between the more distant areas of fin and the source of the heat would be so high. Plenty of heat exchange surface; but not much heat making it out that far.
This is why more or less all contemporary heatsinks started embedding heatpipes some time ago, since that was the only way to get a reasonable amount of heat to the more distant parts of the heatsink.
This 'sponge' is more aesthetically interesting; but I see a lot of surface area that is only tenuously connected to the actual heat source. Newer Intel silicon just doesn't pump out the watts the way the old stuff did, so it might actually work; but I'd be shocked it if works any better than a much more prosaic heatpipe-and-fins design.
Somewhat surprising. This reminded me of a metal aerogel and aerogels are good insulators http://en.wikipedia.org/wiki/A...
basically means that for slower airflow, you need larger gaps for air to flow through. This is why the sponge is bad for heat dissipation, and great for insulation. It's kind of intuitive, but it's nice to have some science backing to it. Having a large surface is good, but it doesn't help if the airflow across the surface is limited.
On a side note, I've been on a quest for quiet cooling since the very early 2000s, incidentally after getting a physics degree. It's mostly in the last couple of years that I've started to see really sensible coolers in the general market. For example, the usual CPU cooler in the olden days had a fan pushing right against the CPU with minimal fins in between, meaning there's a considerable high-pressure centre with no airflow. No one with a fluid mechanics 101 would design crap like that. OTOH, the traditional CPU/mobo setting is a little problematic; first you put the most heat-concentrating element in the middle of everything, and then later you realize it needs cooling. (I'd put the CPU socket on the reverse side and use the case as a huge heatsink...) Now finally the designers have the sense of using a straight sideways airflow, combined with heat pipes. Why the fsck did this take so long?
I used to strive for pure passive cooling, but in the end I don't mind a large, slow fan -- it's enormously better than no fan, and still indistinguishable from other background noises. This is another nice thing to see in cooler designs, from the 1-inch whiner in my first Linux laptop to the 140-mm quiet giants that can easily manage a couple of hundred watts of GPU.
BTW, if you ever need to explain somebody how a heat pipe works, take them to a sauna.
Escher was the first MC and Giger invented the HR department.
Just dial: 0118 999 881 999 119 725 3