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Cooling Processors

  1. Feb 18, 2010 #1
    A friend of mine brought his laptop to me today after it started acting funny, turned out to be over heating problem, since then and I'm thinking.. Why don't they make a cube/container and place the processor in it with liquid Nitrogen around it? Wouldn't that keep it cool forever? I'm not a physicist so its just an idea.
    I found few videos on Youtube of people doing something similar but not really what I have in mind, but they were doing it "for fun".

    What do you physics gurus think?
     
    Last edited: Feb 18, 2010
  2. jcsd
  3. Feb 18, 2010 #2

    mgb_phys

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    LN2 is rather cold, you really only need to cool the CPU to 50C, cooling it to -200C is bit over the top, it puts rather a lot of stress on the components.

    LN2 doesn't have a lot of cooling power, like most diatomic gases it doesn't take much energy to boil, in fact LN2 only provides about 10% more cooling capacity than ice.

    It's also expensive, difficult to handle and slightly dangerous.
     
  4. Feb 18, 2010 #3

    russ_watters

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    It would be expensive and cumbersome to carry liquid nitrogen tanks with you everywhere you take your laptop. Liquid nitrogen doesn't stay cold on its own even without a hot processor dumping heat into it: it boils away, just like water does when you dump heat into it.
     
  5. Feb 18, 2010 #4

    Doug Huffman

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    Air is cheap and reasonably effective as long as the various surfaces and flow paths are kept clean.
     
  6. Feb 19, 2010 #5
    Just thought I'd inject a practical solution for your immediate problem:
    There are "cooling pads" for laptops available for under $20. They are often powered from the laptop's USB port, so battery life will be somewhat reduced.
     
  7. Feb 19, 2010 #6
    Thanks everyone for replying..
    I posted here because I was wondering if phycisists ever thought about using cold liquid gasses like N to cool something like processors, the idea is cool I think, no noisy fans, no worrying about heat anymore.
    But it seems it can't be done, at least for now :-s
     
  8. Feb 19, 2010 #7
    Ln2 is really cold, -200 C, as was expressed already in the thread comments. Imagine you have closed down your computer to a powerless state. Then you'll have to keep the Ln2 cold, that is in its liquid state. If the Ln2 changes to its gaseous state as a result of not cooling it anymore the gaseous pressure in the N2 container on top of the processor will built up and built up to probably a pressure at which the container ruptures due to overload in mechanical stresses. I have an IR detector in my workshop that is cooled to Ln2 temperature. However the Ln2 container is open to air to release the gas that boils off from the Ln2 during cooling of the detector. You might be interested to read some more on the CERN LHC accelerator incident in which large amounts of LHe were put under high heat loads that resulted in extreme mechanical damage to this magnificent machine. Engineers overthere installed a "lot"of gas release valves on the cooling system to prevent similar future accidents. As a last remark consider this simple calculation. Suppose the processor volume is 1 cm3 and produces 1 Watt. The volumetric heat load then is 10^6 watt /m^3. I am really enthusiastic about the ability of a structure to deal with these kind of heat loads. So, any future developments in semiconductors could also take to route to high temperature resistance
    of semiconductors of a new generation, instead of doing large investments in cooling them.
     
  9. Feb 19, 2010 #8

    Doug Huffman

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    Commercial Magnetic Resonance Imaging devices are cooled to superconducting temperatures and maintain huge magnetic fields. How might an emergency shutdown be made without inducing a HUGE current when the magnetic field collapses through the coil and structure? MRI emergency shutdown dumps the USD10e5 He coolant
     
  10. Feb 20, 2010 #9
    Ok, I have been thinking..
    Is it possible to have the processor external and connected to the pc with wire? After all its just a small piece, if that is possible then can you put it in the refredg?
     
  11. Feb 20, 2010 #10

    mgb_phys

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    Unfortunately not.
    The main problem is the capacitance of the wires, each wire takes a certain length of time to 'fill up' with electricity when a signal is applied and to empty when it is removed.
    A wire more than a few mm long takes too long to change state for modern processors - in fact one of the reasons modern CPUs need 1000 pins is to supply signals like clocks to different parts of the chip with low enough capacitance wires.

    There is also the speed of light. Light travels at 1ft/nano-second. Modern CPUs run at 3-4 instructions per nano-second so you barely have time to get a signal a few inches across the CPU - certainly not in and out of the box
     
  12. Feb 22, 2010 #11
    use florinert for a sealed bath that the processor/motherboard inside. outside assy of bath tank is totally covered in heat sink. thermal siphoning would keep the fluid moving. The electronics than would be fluid cooled, and never get dirty. maybe even won't need the fans
    at $500/gal its not cheap though

    dr
     
  13. Feb 24, 2010 #12

    Mech_Engineer

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    CPU cooling is an interesting subject, and there are many ways to accomplish it. Laptops are inherently limited because they don't have room for large coolers, so they usually utilize a combination of heatsinks, heat pipes, and fans that throttle as needed. Most laptops don't need more than a copper heatsink and a fan, as long as the heatsink is properly fitted to the CPU and the fan isn't plugged up with dust. Even larger laptops such as the Alienware M17x which utilizes a high-power CPU and video card only needs well-placed heatsinks and fans.

    For desktops on the other hand, the sky's the limit! It's common to find gamers who utilize water cooling or extra large heatsinks with heat pipes (I personally have used water cooling in the past). In addition, people have used liquid nitrogen, liquid helium, etc for cooling processors in super-exotic applications (like wolrd record-attempt overclocks) but it isn't a permanent solution as you suggest because you have to continually replace the cooling liquid. Liquid nitrogen doesn't stay cold forever, it heats up like any other liquid and will boil off if not replaced.

    A more common "exotic" cooling solution are vapor phase change systems. They are essentially cryogenic refrigeration units with a block of metal on the end to cool a processor. This one for example is capable of keeping the CPU at a constant -50C, for heavily overclocked processors:

    ex-vap-19.jpg
    http://www.frozencpu.com/products/9...78_754_775_1156_1366_939_940_AM2_AM2_AM3.html


    Here's a Tom's Hardware project that uses liquid nitrogen cooling to try and overclock a CPU to 5GHz:
    aufmacher_en.jpg
    http://www.tomshardware.com/reviews/5-ghz-project,731.html
     
    Last edited: Feb 24, 2010
  14. Feb 24, 2010 #13

    Mech_Engineer

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    No need to use Fluorinert, you can just use vegetable oil like Tom's Hardware did :tongue2:

    aufmacher.jpg
    http://www.tomshardware.com/reviews/strip-fans,1203.html
     
  15. Feb 24, 2010 #14

    mgb_phys

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    A combined PC and donut maker - mmmm !!!
     
  16. Feb 26, 2010 #15
    I like that line of thinking, PC's that also make food as you use them
    how about a plate above the processor, with a peltier in between.
    use a plate that is about 5" x 5"
    and
    shazammmm.....surfin the net with grilled cheese backup...

    hey one of my first "puters" (think it was a trash 80) put out enought heat off the power supply to keep your coffee warm...lol

    jr
     
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