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The Fanless Spinning Heatsink 380

An anonymous reader writes "There's a fundamental flaw with fan-and-heatsink cooling systems: no matter how hard the fan blows, a boundary layer of motionless, highly-insulating air remains on the heatsink. You can increase the size of the heatsink and you can blow more air, but ultimately the boundary layer prevents the system from being efficient. But what if you did away with the fan? What if the heatsink itself rotated? Well, believe it or not, rotating the heat exchanger obliterates the boundary layer, removes the need for a fan, and it's so efficient that it can operate at low and very quiet speeds. That's exactly what the Air Bearing Heat Exchanger, developed by Jeff Koplow of the Sandia National Laboratories, has developed. It's even intrinsically immune to the build up of dust and detritus!"
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The Fanless Spinning Heatsink

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  • by Bill_the_Engineer ( 772575 ) on Tuesday July 12, 2011 @10:21AM (#36733492)
    I think a better description would be a heatsink that is a fan or probably more accurately an impeller but without the tube enclosure.
    • .. it seems like a great invention, trully ground-breaking if it works. All we have to do now is wait for the patent wars to be over (suddenly $BigCorp and $PatentTroll "discover that this infringes on their innovations somehow and some such"), and by 2054 this will be a commonplace in cooling.

      Now I wander if the guy was under contract- if he was, he will probably get nothing but his salary out of it. One of my friends is family with the guy that invented the dictionary in cellphones; but since he was under

    • And wouldn't the friction of the thing spinning generate heat as well? I'll admit i just looked at the pics but heatsink compound is made for heat transfer NOT lubrication so I don't see how this would be such a great improvement, not to mention having it spin right on top of the CPU would have me worried about it putting sideways pull on the pins, as anyone who has built boxes knows those pins are teeny tiny and don't take much to bend so if the lubricant you used started to get sticky I could see this thi

      • Re: (Score:3, Informative)

        From TFA, highlighted for your convenience...

        The cooler consists of a static metal baseplate, which is connected to the CPU, GPU, or other hot object , and a finned, rotating heat exchanger that are cushioned by a thin (0.001-inch) layer of air. As the metal blades spin, centrifugal force kicks up the air and throws it up and outwards, much like an impeller, creating a cooling effect.

        • I wonder how jostling of the PC case might affect this 'bearing'? Is it possible that the spinning disc would then impact the static metal base plate?

          Seems like this concept would already have been dealt with via spinning hard disk platters, but those don't weigh nearly as much as a heat sink and are segmented out specially with shock absorbers in the HD enclosure.
      • by Dr_Barnowl ( 709838 ) on Tuesday July 12, 2011 @11:57AM (#36735244)

        The bearing between the fan and the plate is a very small air gap. Because it's small, and because it's constantly being churned around, it's thermal resistance is low.

        Because the movement fan part destroys the normal zone of still air around radiator fins it dissipates heat more quickly and efficiently.

  • Doesn't there still need to be a stationary connection to the rotating heatsink since the CPU is stationary? And if that's the case, how does this help prevent the boundary layer? Seems like one would still be able to form between the CPU surface the the rotating heatsink.

    I'm no scientist, however, so I'm probably making a false assumption. But I am curious how this alleviates that boundary layer...

    • by S.O.B. ( 136083 )

      The article and the PDF will answer all your questions.

      • To be fair, the article doesn't address that question at all. Haven't read the PDF, though, as I'm at work and not currently able to. Anyone care to paraphrase, or shall I wait until I get home?
        • Comment removed based on user account deletion
          • by Locutus ( 9039 )
            thx, I didn't get to read the details yet and this explains it. In a conventional system, there's static air on the heatsink which is, static and and so it insulates. They seemed to have moved that static air boundary to the air gap between the rotating heatsink and the surface which is attached to the CPU. The air gap is so small that the friction between the air and the two surfaces moves the air and voila, no static air so no insulating air and better heat transfer. nice.

        • Essentially, they claim the really thin (~0.03mm) layer of air between the stationary plate and the rotating heatsink is thermally conductive and agitated by the rotation, so no static boundary layer.

        • Re:I'm curious... (Score:5, Informative)

          by goofy183 ( 451746 ) on Tuesday July 12, 2011 @10:57AM (#36734104)

          I had the same question but it is very well addressed in the PDF:

          During operation, these two flat surfaces are a separated by a thin (~0.03 mm) air gap, much like the bottom surface of an air hockey puck and the top surface of an air hockey table. This air gap is a hydrodynamic gas bearing, analogous to those used to support the read/write head of computer disk drive (but with many orders of magnitude looser mechanical tolerances).
          Heat flows from the stationary aluminum base plate to the rotating heat-sink-impeller through this 0.03-mm-thick circular disk of air. As shown later in Figure 18, this air-filled thermal interface has very low thermal resistance and is in no way a limiting factor to device performance; its cross sectional area is large relative to its thickness, and because the air that occupies the gap region is violently sheared between the lower surface (stationary) and the upper surface (rotating at several thousand rpm). The convective mixing provided by this shearing effect provides a several-fold increase in thermal conductivity of the air in the gap region.

          The PDF also goes into how this tech could have serious applications in things like home AC and refrigerator heat exchangers as well.

        • There is 0.3mm of air between the base plate and the spinning impeller. Because this air gap is thin, wide and sheared (i.e, the top part is spinning and the bottom part isn't - so you get lots of convection), the thermal resistance of the air gap is actually very low.

        • your work blocks PDFs from but you can browse slashdot? or do they just restrict all PDFs?

    • But I am curious how this alleviates that boundary layer...

      Maybe it's a side-effect of using an air bearing? Little rotating concentrated jets of air blowing down on the hot metal plate....

    • by Zerth ( 26112 )

      The heat transfers through the air bearing, which is very thin and in the paper is dry nitrogen gas, IIRC.

    • Re:I'm curious... (Score:4, Insightful)

      by tibit ( 1762298 ) on Tuesday July 12, 2011 @10:53AM (#36734040)

      Nope, the "connection" is a thin (1E-5m) air gap experiencing high shearing and thus providing very low thermal resistance. The gap's thermal resistance contributes very little (on the order of 10%) to the overall thermal resistance of the cooler. It is a truly revolutionary design, no shit here.

    • Re:I'm curious... (Score:5, Informative)

      by canajin56 ( 660655 ) on Tuesday July 12, 2011 @10:54AM (#36734058)

      Yes, a layer of air does form between the heat spreader base, and the base of the rotating heatsink. This is called an air bearing. It's extremely thin, and for that reason an excellent thermal conductor even though it's conducting heat poorly. You see, it has a surface area of 100 cm squared, but it is less than 0.03 mm thick. So, heat transfer is inefficient, but its so thin as to be negligible.

      And no boundary layer forms (well, it does but it is reduced by a factor of 10) on the fins because they are rotating. The equations for fluid dynamics are quite different between an inertial reference frame and a rotating one. Basically, the fluid cannot settle into little pockets because the (fictional) centripetal force is pushing it outwards along the fin channels.

      • by kybred ( 795293 )

        Basically, the fluid cannot settle into little pockets because the (fictional) centripetal force is pushing it outwards along the fin channels.

        Oblig XKCD []

    • No, there doesn't need to be a stationary connection.

      Here's the problem the boundary layer presents: The air in the boundary layer, by definition, has zero velocity relative to the solid surface, so the only way for heat to leave the surface is by conduction across the boundary layer. (Well, I'm ignoring radiation here, but I don't think that's very much.) The thermal conductivity of air is low, so it presents a substantial thermal resistance.

      The effect of the Sandia device is not to eliminate the bounda

  • Homeless (Score:4, Funny)

    by phrostie ( 121428 ) on Tuesday July 12, 2011 @10:26AM (#36733578)

    But think of all the homeless Dust puppies!!!

    have you no shame?

  • That's exactly what the Air Bearing Heat Exchanger, developed by Jeff Koplow of the Sandia National Laboratories, has developed.

    So I get it was not Jeff Koplow who developed it, but the Air Bearing Heat Exchanger did develop it. The Air Bearing Heat Exchanger in turn was developed by Jeff Koplow.

    Oh, and BTW the link was missing a PDF warning.

  • Well this idea isn't new at all. Back in the 1910's aircraft engineers were trying to produce engines that could be cooled without heavy water jackets and radiator cooling systems. Putting cooling fins around the engine cylinders and block to let the passing air cool the engine worked, but not well enough given the state of metallurgy at the time. One solution was a rotating radial engine. In this configuration the crankshaft of the engine was bolted to the firewall and the block spun around with the cr

    • by Chrisq ( 894406 )

      A vegetable based oil was used (which had a laxative effect on the pilot!).

      Or was it just coming up against the Red Barron?

    • In these "old" engines, the cooling block itself did not move, rather the engine it was attached to moved. The equivalent would be for an entire PC to spin in for radiators attacked to it to be cooled. This would be highly inconvenient for any cat owners as well as make it even harder to plugin that USB cable.

      • by vlm ( 69642 )

        The equivalent would be for an entire PC to spin in for radiators attacked to it to be cooled. This would be highly inconvenient for any cat owners as well as make it even harder to plugin that USB cable.

        Standard socket and packaging technology is going to have issues with the centrifugal force and vibrations. Spinning the whole gadget and doing all the connections with sliprings for power (or solar cells and searchlights?) and bluetooth for I/O MIGHT actually work... Need to research bluetooth doppler sensitivity first...

    • At last an intelligent post on this subject - much of the above falls into RTFA land. Though part of the benefit arose simply from the fact that the engine continued to be cooled even when the air speed was close to zero, and another part because both sides of the cylinder were cooled, whereas in a conventional engine only one side was cooled. That is why the famous Moto-Guzzi single could run with such low distortion; the horizontal cylinder was air cooled on all sides, even better than the BMW twin.

      In th

  • I would imagine replacing the 0.0254 mm of air with a ferrofluidic seal [] would increase the efficiency even further. A chip is not damaged by a permanent magnet and since the RPM is low it will not require a very strong magnet. The seal would be a good thermal conductor (somewhere around thermal paste).
  • I like the "protective wire mesh container". Tell me it's not an office trash can.
  • by metalmaster ( 1005171 ) on Tuesday July 12, 2011 @10:56AM (#36734100)
    I thought a long standing goal of PC manufacturers was to do away with moving parts. I dont think fans will go away anytime soon as long as they are cheap [] to replace. From the comments hear I'd assume this heatsink spins on a platter essentially taking the place of the fan. What do you do when it fails? Can you replace it for less than $10?
    • Kinda depends on which PC manufacturers. Really, there are two diametrically opposed problems being solved: either you're going for the silent, no-moving-parts, low-cost, low-maintenance approach (commodity PCs, home-entertainment appliances, etc.)... or you're going for the balls-to-the-walls, maximum FPS, humongo display resolution enthusiast machines. In the former case, yeah, this technology probably wouldn't be appropriate (in its current incarnation). But for the latter? You always have serious heat d
      • by EvanED ( 569694 )

        Kinda depends on which PC manufacturers. Really, there are two diametrically opposed problems being solved: either you're going for the silent, no-moving-parts, low-cost, low-maintenance approach (commodity PCs, home-entertainment appliances, etc.)... or you're going for the balls-to-the-walls, maximum FPS, humongo display resolution enthusiast machines.

        I definitely wouldn't group that first category all together. Silent/no-moving-parts really shouldn't be together with low-cost, and I'm not sure where low-

  • Don't some lawn mowers have heat sinks like this that spin atop the engine?

    Anyway, I'm much more interested in the air conditioner applications of this than electronics use. I like the idea of a quieter, 30% more efficient air conditioner/heat pump. Great article.

    • That's it, really. Small IC engines are usually air cooled using a ducted fan. My rotavator has one. As I note in a post above, IC engines don't really have the problem because the path from heat to sink is short and the power density is quite low, and the main benefit of well designed fan cooling is that the cooling is even around the cylinder. The fin depth on a Honda 50cc engine is less than that on many CPU heatsinks.
  • wonder if the barrier is caused by the constant, unidirectional flow of air from a fan?
    while it's hardly an efficient/practical design, would you achieve the same efficiency if you moved a fan around the heat sink?

  • We don't need a lot of big government creating new technology and improving our energy consumption!
  • This is awesome. It appears to be using similar principles and design to Tesla's turbine! (From wikipedia, which doesn't have a good picture of the innards) "The Tesla turbine is a bladeless centripetal flow turbine patented by Nikola Tesla in 1913. It is referred to as a bladeless turbine because it uses the boundary layer effect and not a fluid impinging upon the blades as in a conventional turbine"

  • RTFA (Score:5, Insightful)

    by xtieburn ( 906792 ) on Tuesday July 12, 2011 @12:02PM (#36735334)

    I know its said a lot and should be common knowledge but I think it pays to stress it more strongly on occasion. This seems like an ideal time, READ THE FUCKING ARTICLE.

    Several posts now, numerous mod points and dozens of follow ups all frankly making complete asses of themselves ironically complaining about how the IQ of /. has dropped while they make angry complaints and rants about the story that are fully addressed in the documentation.

    and if you think that the fact that the summary screwed up is still a good sign of /. intelligence drop then you really need to look right back in the archives because bad summaries have been around on /. and virtually everywhere else pretty much from the beginning. Unsurprisingly the people posting the stories dont have total knowledge of the often fairly complex material posted and they screw it up good and proper on occasion. Which is probably why you should be judging the posts on the documents they link to and not the quickly thrown together summary by an admitted layman. Anything else is ironically a really stupid thing to do.


    (and no this doesnt mean the documentation is flawless but make commentary on that, not the summary, it will raise that intelligence level a lot of you are so eager to whine about.)

  • by xkr ( 786629 ) on Tuesday July 12, 2011 @12:13PM (#36735486)
    If you read the complete PDF from Sandia, the author points out that the boundary layer inefficiency "doesn't apply to laptops." Here is the quote from the paper:

    The exception to this rule is lap top computers, where available electrical power is extremely limited. In this special case, CPU clock speeds and fan rotor speeds are reduced to conserve power, albeit at the expense of CPU performance. At these low fan speeds the residence time of air in the heat exchanger is greatly extended, resulting in much higher exhaust air temperatures.

  • by demonbug ( 309515 ) on Tuesday July 12, 2011 @01:01PM (#36736156) Journal

    My first thought looking at the linked paper was, "January 2010? Why hasn't this been all over the place if the results are so promising?"
    But there could be lots of reasons for that. Just sort of popped out.

    Another question that comes up is overall system efficiency. One advantage of the current fan + heat sink paradigm is that in addition to moving air across the heat sink, which is not terribly efficient, the fan also serves to mix the heated air around the heat sink with the larger reservoir of surrounding air. They don't really directly discuss it, but my impression is that their design would result in very little large-scale mixing; one of the efficiency advantages is that they aren't moving large amounts of air around. It seems that in a setting like a CPU cooler this might be a non-issue, as you would still presumably be using case fans to move air through the case (exchanging the reservoir); but in something like an air conditioning unit, it seems like it would become limited by convection for larger scale heat transfer - or require an external fan for air exchange.

    Basically, my concern is that while this method might be very efficient in moving heat from the base plate to the air in the immediate vicinity, you would then have the problem of heat building up around it. Perhaps not an issue where you have a small-scale device open to a large, room-temperature environment (or where you already have something in place to move air around, like a computer case), but it seems like it could be an issue moving to something like a residential air conditioner.

    Still, it appears to eliminate the boundary layer problem, so you could use a pretty efficient, large, slow-moving fan for air exchange - so probably more efficient than blowing high-speed air across a heat sink, but something that would need to be considered in a full implementation.

Never buy from a rich salesman. -- Goldenstern