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OT: CPU heatsink "heat pipes"

Discussion in 'Electronic Design' started by John Doe, Jan 4, 2006.

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  1. John Doe

    John Doe Guest

    Is it hype, or is it technology? I'm wondering what is the
    usefulness of "heat pipes" in CPU heatsinks?

    Seems to me that a "heat pipe" is not a pipe in the ordinary sense
    of the word, so it isn't going to transport anything the way a pipe
    does. I guess it is a solid rod of copper that conducts heat about
    the same as any other shaped copper conducts heat. Would its use
    have to do with the shape of the heatsink, perhaps allowing the
    heatsink to fit into a narrower space or allowing an easier/cheaper
    connection between the CPU contact area and the heatsink fins or

    Thank you.
  2. Tweek

    Tweek Guest

    Heat pipes are not solid. They have a liquid in them that is constantly
    changing from a liquid to a gas and back. As it does so it transfers the
    heat from the end connected to the cpu to the end at the cooling fins. They
    are most commonly used in laptops so the heatsink and fan can be thin and
    located in a convenient location.
  3. John Larkin

    John Larkin Guest

    Actually, about 100 times better than copper.
    It allows a huge heatsink area to be thermally coupled to a small CPU
    chip. Water cooling can do that, too.

  4. Conor

    Conor Guest


    I'm wondering what is the
    Works on the same principle as a radiator on a car.


    I'm so grateful to the USA for their contribution to the war on terror.
    After all, if they hadn't funded the IRA for 30 years, we wouldn't know
    what terror was.
  5. John Doe

    John Doe Guest

  6. It transports heat, and does so by fluid transport.
    Hollow, like a pipe, hence the name.
    It doesn't conduct heat the way a solid does, it transports it via fluid
    flow, and is orders of magnitude better than copper.
  7. Well, there are some similarities but fundamental differences. A heatpipe
    uses the heat itself, combined with either gravity or capillary action, as
    the transport mechanism and, so, doesn't require a mechanical pump. It also
    operates on phase change whereas water boiling in a car cooling system is
    bad news.
  8. Ian Stirling

    Ian Stirling Guest

  9. Never Mind

    Never Mind Guest

    Only for the "heatsink" part of the system; the heat pipe element is
    something completely different.

    I'd stick to driving trucks if I were you.
  10. John Doe

    John Doe Guest


    It's been very informative, thanks to all of the replies. The most
    important information seems to be that the heat pipe is
    exceptionally conductive.
  11. Kryten

    Kryten Guest

    Fundamentally an enclosed tube with a bit of fluid in it
    Fluid boils at one end, condenses at the other, then travels back through
    gravity or capillary action along the tube wall.

    The vapour can carry heat much faster than solid copper can conduct it.

    The tube often has a partial vacuum so the fluid boils at around the
    temperature the cooled device is intended to run at.
  12. Conor

    Conor Guest

    Do you know what convection is? The first car engines didn't have


    I'm so grateful to the USA for their contribution to the war on terror.
    After all, if they hadn't funded the IRA for 30 years, we wouldn't know
    what terror was.
  13. Conor

    Conor Guest

    Really? Care to explain how? It's using a moving fluid to transmit heat
    away then passing the liquid via pipes through fins to dissipate the
    heat. I wonder how a car cooling system works...oh yeah, the same.
    I'd stick to working in Mcdonalds if I were you.


    I'm so grateful to the USA for their contribution to the war on terror.
    After all, if they hadn't funded the IRA for 30 years, we wouldn't know
    what terror was.
  14. Guest

    Only half right. The last couple of steps in manufacturing a heat-pipe
    involve compeletely evacuating it, ten distlling in the desired amount
    of theworking fluid - usually water - then sealing off the tube.

    The only vapour in a good heat pipe has come from the evaporation of
    the working fluid, so that the "boiling point" of the working fluid is
    always pretty much the temperature of the coolest point along the heat
    pipe. You might get some pressure drop along the heat pipe as the
    vapour flows from the hot spot from which it is boiling off to the
    coolest point where it condenses, but this doesn't usually amount to

    A bad heat pipe - which hasn't been properly evacuated - doesn't work
    too well at temperatures below those required to make the vapour
    presure of the working fluid a good bit higher than the partical
    pressure of the residual (non-condensing) gases.
  15. Sjouke Burry

    Sjouke Burry Guest

    A heatpipe is filled with a wick to transport fluid to the hot end,
    from the cold end,at the hot end the fluid evaporates, goes to the
    cold end ,condenses ,is sucked up by the wick and fed back to the
    hot side. Evaporation takes a huge amount of heat,at a very small
    change of temperature,(as in boiling water),so you can get a lot
    of heat out of a small place, and bring it to a place were there is
    room to get rid of it.
    In one type of laptop I had open,they used the whole area below
    the keyboard to get rid of the heat.
    So the pipe really ships gas in one direction , and fluid in
    the other(with the help of the wick).
  16. budgie

    budgie Guest

    Please read David Maynard's response. It's all about phase change
    (liquid/vapour) and NOTanything like an automotive cooling system unless that
    latter is in distress.

    Maybe a google on "heat pipe" would assist your grasp.
  17. budgie

    budgie Guest

    No it ISN'T.
    Wrong again.
  18. Rich Grise

    Rich Grise Guest

  19. Rich Grise

    Rich Grise Guest

    No. In a car engine/radiator, the working fluid is the liquid. The
    heat transfer medium is the liquid. The mechanism is conduction;
    the "radiator" actually cools the fluid mostly by conduction. (to
    the air, of course.)

    In a heat pipe, the working fluid is vapor. The working fluid boils
    at the hot end and condenses at the cold end, then wicks back to
    the hot end as liquid. The mechanism of heat transfer is phase

    Hope This Helps!
  20. Tim Williams

    Tim Williams Guest

    Wait-- water? Vacuum? These are *atrocious* refrigerants! Wouldn't it
    have to be a common refrigerating gas, such as perhaps a medium freon, or
    butane? Under sufficient pressure of course. Pressure then varies with
    temperature, as with any compressed liquified gas.

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