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Alt: CFM calculator to get rid of HEAT (TDP or WATTS)

Discussion in 'Nvidia' started by Skybuck Flying, May 18, 2011.

  1. Alternative thread in case original thread don't produce no results or some
    miss it ! ;) =D

    Important topic ! ;) =D


    I'm curious if it's possible to build a powerfull PC/iCore/GPU/Cuda PC
    without getting into heat problems ! ;)

    For example CPU has about 30 TDP (which is close to watts, otherwise find
    watts listing) and GPU could have as much as 200 to 300 TDP (watts) (top
    model for maximum bandwidth).

    Additional watts for memory( 20 watt ? just guessing ;)) /motherboard (10
    watt ?)/4 harddisk (60 watt*4=240)

    Let's say 800 watts.

    How much CFM would be needed to get rid of all that heat ?!?

    A CFM heat (PC) calculator would be most handy... maybe somebody can
    make/program it.

    What would be good formula's to use ?!? ;)

    Skybuck =D
    Skybuck Flying, May 18, 2011
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  2. Skybuck Flying

    Paul Guest

    CFM = 3.16 * Watts / Delta_T_degrees_F

    Say room temperature is 72F, case air temperature target is 90F,
    computer watts is 200 watts.

    CFM = 3.16 * 200 / (90 - 72) = 35CFM

    You can get around three times that airflow rating from a fan like this,
    but you don't want to be sitting next to this. The fan draws
    12V @ 1A and should not be connected to the motherboard header.
    You can run this off a Molex drive connector.


    DDR3 memory DIMMs are around 2W. Hard drives are less than 12W. Your
    800W number needs to be reworked.

    Paul, May 18, 2011
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  3. Hmmm... could be really simple...

    Wikipedia shows conversion chart:


    1 atmosphere-cubic foot per minute = 47.820 074 682 24 W

    Which is probably close to 48 Watts.

    But this is atm-cfm and not cfm hmm... not sure if that is same thing... but
    for now I'll go with it ;)

    So (800 * 60) / 48 = 1000 CFM needed ! ;) =D

    Let's see if antec case is sufficient lol:

    http://www.antec.com/pdf/manuals/1200_EN manual.pdf

    It's about 240 CFM...

    So there is no way that the antec 1200 case would be able to cool such a
    system sufficiently.

    Yes perhaps the graphics card would output a little bit of air as well...
    but it's waaayyyy too little.

    And this manual probably assumes at maximum operating fan speed... so let's
    divide 240 by 2 is 120 CFM... and let's divide it one more time because of
    dust is only 60 CFM.


    Well it's pretty clear where this is going:


    Skybuck ;)
    Skybuck Flying, May 18, 2011
  4. It might seem "we computer people" are getting fooled/scammed by
    specifications ((unrealistic)CFM).

    I sure hope that's not the case because then all of your calculations are

    and with "your" I mean everybody that used CFM.

    You might want to read up on this stuff:


    "real cfm" ;)

    For now after a quick glance I am thinking my atmosperic calculations might
    actually be closer to the truth ;)

    Time will tell ! ;) =D

    Skybuck Flying, May 18, 2011
  5. Another nice website:


    Mentions pressure must be added to the equation of "CFM" ;)

    Manual of antec1200 mentions "static pressure".

    (it's something like 0.something ! yeah ! lol)

    Gonna look that up ;)

    Skybuck Flying, May 18, 2011
  6. Skybuck Flying, May 18, 2011
  7. Skybuck Flying

    Rob Guest

    Paul's calculation is correct. He knows what he is talking about.
    Rob, May 18, 2011
  8. Skybuck Flying

    Paul Guest

    That's the only equation I know of, off hand. I'm not a thermal engineer,
    and cribbed that off a web page that detailed how to put a computer
    into an enclosure, and ensure it got enough cooling air. I expect
    there is some room for using pressure curves for the fan, but I
    don't know the first thing about that. I had an engineer at work,
    who used to do that part for us. When you work in a big company,
    you're generally "stuck in a silo".

    Paul, May 18, 2011
  9. Skybuck Flying, May 18, 2011
  10. Skybuck Flying, May 18, 2011
  11. Skybuck Flying, May 18, 2011
  12. Most interesting part so far, and most interesting website so far:


    It mentions CFD analysis.

    Why calculate one little simple fokking formula if you can simulate the
    whole system ! LOL.

    What hopefully CFD analysis software ! ;) =D


    Csomething Fluid Dynamics LOL.

    Skybuck Flying, May 18, 2011
  13. Skybuck Flying, May 18, 2011
  14. This one also seems kinda cool but a bit old, but that could be an
    adventage, since I am on a PIII 450 mhz ;) and best of all it's free, alas
    only for MAC OS and Linux:


    Could still be interesting though.

    Skybuck Flying, May 18, 2011
  15. Skybuck Flying, May 18, 2011
  16. Skybuck Flying

    Rob Guest

    I know what you mean Paul. I do have windows here, but they
    have bars on them! :eek:)
    It's easy to get hung-up about system cooling, especially with
    heat being the biggest killer of hardware. I just configure
    things so that hard drives have airflow over them, stay
    below 40C and that everything else (particularly CPU and GPU)
    stays within spec'd temps when pushed hard. Unless it's an
    overclocked system, that normally just means a standard 120mm
    fan drawing air in at the front and same extracting at the back,
    with perhaps an extra fan directing air across the HDs if
    they are poorly positioned within the case (as they often are.)
    Because PSUs generally also have fans, I'd assume this leads
    to a slight negative air pressure but that's not something
    that seems to have any measureable effect in my experience
    (eg I tried 3 intake fans as an experiment a few years ago
    when I was overclocking those P4 Prescott roasting devices!)
    Cooling has become much less of an issue with modern hardware -
    even high-end GPUs dissipate much less power these days.
    Rob, May 18, 2011
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