Case fans. Which way should the air flow?

Discussion in 'Computer Games and General Discussion' started by Harsky, Sep 21, 2010.

Sep 21, 2010
  1. Harsky
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    Member Harsky Madmin

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    Bought a new case and also 12cm back case fans. I originally had plans on having TWO fans where one sucks in cool air and another to blow out the inside air. Unfortunately, the result was a VERY noisy whirring PC so I decided to just stick with the single back fan. My question is, is it better to have something blow air in or something to suck the air out?
     
  2. Joe88

    Member Joe88 [λ]

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    you want it moving through the case

    ex.
    air gets sucked through the front
    heat from various components (gfx card, cpu hsf, chipsets, ect...) gets expelled through the back
     
  3. Originality

    Member Originality Chibi-neko

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    If the fan is positioned at the back of the case (i.e. behind the CPU heatsink) then you should have the fan sucking air out of the case (i.e. an exhaust fan). If it's positioned at the front or side of the case, you should have it sucking air into the case (i.e. an intake fan). Ideally, you want both to create air-flow that always sucks in fresh air to cool the parts and sucks the hot air back out.

    Word of warning, if you have an exhaust fan but no intake vents (i.e. holes in the front or bottom that let air in) then you may just suffocate the parts, which won't help cooling at all. Likewise, if you have an intake fan but no exhaust vents (nearly every case should have some grills on the back that act the same), then you'll just be sucking dust into the computer and not actually cooling it. That's typically why both are needed.

    If you find the fans you're using too noisy, consider buying fans with lower speeds. Scythe do case fans for all sorts of situations.
     
  4. Scorpei

    Member Scorpei GBAtemp Maniac

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    Or just hook up an resistor / hooking up the fans to 5V if they still spin up. Personally built my server24/7 next to my head machine with:
    1x23cm side fan (Want to add another)
    1x120mm cpu cooling (on my scythe kama angle)
    1x80mm directly next to that fan blowing the air from the kama angle outside the case
    1x140mm in my Nexus power supply (load regulated) (value 430, quitest drive I ever owned next to my fortron passivly cooled one of course)
    (and in theory, and I have had that setup, 3 more 80mm fans of which one was front low sucking, one videocard cooling and one an exhaust above the PSU)

    All of which run at five - seven volts, depending on when I felt they were quite enough
     
  5. Santee

    Member Santee Jalapeño

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    Intake fans go to the bottom so that the air rises and cools and the outake fans should be at the top because hot air rises.
     
  6. Originality

    Member Originality Chibi-neko

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    I think you'll find the majority of cases don't actually have fans at the top/bottom. Until a few years ago, most cases went without any fans at all except in enthusiast systems which had an exhaust fan on the back and maybe a shroud on the side to help the CPU heatsink. Now computers are always very hot so you get all sorts of fan arrangements in modern cases. They always have at least one large (120mm usually) fan at the back, often have at least one large fan at the top, and often have at least one fan located somewhere in the front or bottom (front being more effective) and the side (to blow on the GPU). Still, not every modern case opts for a fan on the top/bottom because front/back still work very well - suck in cold air from the front, use the heat from the GPU and CPU to rise, and expell the hot air out the back.

    There is only one case which is actually designed in the way you described - with an array of intake fans on the bottom and exhaust fans on the top "because hot air rises" (although I can't remember the name of it off the top of my head). The first version of it didn't actually perform too well and cable management was quite a nightmare, because the motherboard had to be rotated 90 degrees (i.e. the cables for the graphics card and the rear I/O panel were located at the top). The second version of it improved on the idea and made cooling more efficient, taking into account the needs of the reorientated GPU and CPU (which were still rotated 90 degrees). I still wouldn't use it though unless it proved advantageous to have the graphics ports and rear I/O panel easily accessible from the top (a situational advantage at best).
     
  7. Harsky
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    Member Harsky Madmin

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    The main problem seems to be focused on my 9800GT graphics card. I bought a new case because so now it has more clearance from the bottom of the case compared to my last case but it still heats it up a little. Does anyone have any experience with a product like this?

    http://www.crazypc.com/products/5303.html

    As for the, "hot air rises" debate, for some reason, the heat seems to be mainly focused on the bottom part of my case.
     
  8. Originality

    Member Originality Chibi-neko

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    Typically the GPU is the hottest part of the system, which is why many cases have a side fan that can blow air directly onto the graphics card. In cheaper cases, hot air builds up in the bottom of the system because there's usually nowhere for that air to go. Some cases make use of the power supply to remove this hot air, but tht only works if the PSU is designed in that way - and is located on the bottom of the case. A PCI fan like that would fit the bill - sucking some of that hot air out, although I imagine it'd only be effective if there's also some form of inlet or intake fan to blow fresh air back into the machine - usually located on the front. EDIT: Otherwise, you may end up suffocating the GPU.
     

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