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Making a stronger air flow using 2 fans

  1. Feb 1, 2008 #1
    I want to know what setup is best to create a stronger or faster air flow.
    I want to place 2 fans side by side you have a second fan on front of another. because I already tried running both fans at the same speed the result is the air flow or air current is not strong somehow theres a conflict in air rotation or something, so I want to know what is the best setup.

    what about making the second fan spin slower? would that work?
     
  2. jcsd
  3. Feb 2, 2008 #2

    LURCH

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    Science Advisor

    No, if you make the second fan turn slower it will act as a break and slow down the air flow. You might try having both fans turn at the same speed, but angle the blades on the second and much more steeply. Because the air coming into the second fan is already in motion, you can angle the blades so sharply that it would burn out the motor if the fan were trying to move air that started out stationary. I should, however, point out that this will not work within an airtight enclosure. At least fans inside of ducting? If so, then you will get your best results by placing the fans side-by-side. Also, are you trying to get faster airflow, or greater volume? For greater volume, leave the ducting as wide as the two fans in parallel. For faster wind speeds, use narrower ducting, but this will result in a decrease of overall volume, as it will increase resistance.
     
  4. Feb 2, 2008 #3
  5. Feb 3, 2008 #4
    Agreed.

    Isn't the same as saying the second should be faster?
     
  6. Feb 3, 2008 #5

    dst

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    Believe me, I've tried this ;)

    You need to actually speed up the fan (not 2 fans) physically, using for instance, a 24V supply (not all fans can take it and life span is reduced drastically).

    Adding a second fan will increase the force the air is blown in, but it will NOT speed up anything (in terms of cooling).
     
    Last edited: Feb 3, 2008
  7. Feb 3, 2008 #6

    Dale

    Staff: Mentor

    A fan that is not designed for it will not work efficiently in series. You are much better off arranging the fans in parallel. Your airflow will not have a higher velocity, but it will have a higher volume. For cooling a PC that is probably more important anyway.
     
  8. Feb 3, 2008 #7

    russ_watters

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    Staff: Mentor

    120mm is a pretty big case fan. For a while, I had one sitting on the side panel of my computer blowing directly onto the motherboard. AFAIK, you can't mount them anywhere else. And it doesn't matter anyway, because one pushes enough air that you won't get the interior of the case any cooler by adding more.

    The general theory on case fans, though, is to have the case slightly positive in pressure so that you don't pull dust in through every little crack.
     
  9. Feb 3, 2008 #8
    just a question

    just a little question.
    If the air from the fan does not cool the object enough. Is the air temperature too warm?
    maybe the air needs to be cooled? sorry for this but when i used a cheap old air conditioner and on a cabinet where the outside temp was about 36-40 c. The heat from the power supplies increased the temps. I had 2 6 inch fans blowing into the cabinet but this was not enough for the whole cabinet. But by cooling the air going in reduced the entire cabinet tempuratures and all the electronics started working properly.
     
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