Optimal air flow in case

[dpk33]

I have a Corsair Air 240 with 3-4 case fans. I'm not sure how to position them for optimal airflow. The following is a picture of my case and the blue rectangles are where I'm able to place 120mm case fans. Right side is front of the case.

 

[Spydermag68]

Where is your power supply? In a lot of new cases have the PS on the bottom instead of the top. From what I know you want positive air pressure inside the case. So two fans in the front of the case and then one on top to blow the hot air out.

In my new case I just got I have a place for side fans over the GPU. I have court out a piece of plastic to cover this since my computer will be in an area where hot air could re-enter from the side. The top of my case has a place for two 140mm fans but I am installing only one. I also have a small USB fan sitting on top of the case to help blow air back out of it's computer hole in my desk.

 

[Yuriman]

Positive pressure is useful for keeping dust out if you have filters, but I've found that in cases that have just one fan, blowing out results in significantly better temperatures than one blowing in, and in a case with two, one in and one out is best.

If your case is on the floor, you don't want fans on the bottom blowing in (because of dust/hair).

Regardless, I'd have two on top blowing in, and two on the bottom blowing out. You definitely want a fan near the video card doing something, as it's doubtless the largest source of heat in your case, and having that air immediately removed (and in a direction that discourages dust from entering your case) seems ideal.

 

[Blain]

No configuration will keep out any significant amount of dust.
Don't fight natural convection...
Two top blowing out, two front blowing in, two bottom blowing in.
If there is a fan mounted on the rear, it should be blowing out.

 

[Essence_of_War]

SPCR has an excellent article about air flow and noise for a gaming build in this exact case. It might be worth taking a look at their notes.

http://www.silentpcreview.com/article1430-page1.html

They are, as you might guess by the name, obsessed with maximum performance at minimum noise levels, so YMMV, but the best configuration they tried can be found here:

http://www.silentpcreview.com/article1430-page11.html

where basically they turned the case on its side, and backwards. If that makes sense:

Edit: Also note that they are using an after-market GPU cooler. They had some clearance + noise issues with the 970 they started with. The whole write-up is really quite fascinating.

 

[Yuriman]

No configuration will keep out any significant amount of dust.
Don't fight natural convection...
Two top blowing out, two front blowing in, two bottom blowing in.
If there is a fan mounted on the rear, it should be blowing out.

Convection's addition to the equation is practically zero.

The convective air flow volume generated at a certain height by the hot or cold surface can be calculated as

Q = 0.019 [g (te - ts) / (273 + te)]0.4 l1.2

te = temperature environment
ts = temperature surface (heatsink, in this case)
Volume is calculated relative to the size of the surface (heatsink area, in this case)

I'm not going to make any specific assumptions, but ballpark figures produce numbers in the area of a tenth of a cubic foot per minute, which is practically irrelevant the moment you have a single fan.

 

[dpk33]

Positive pressure is useful for keeping dust out if you have filters, but I've found that in cases that have just one fan, blowing out results in significantly better temperatures than one blowing in, and in a case with two, one in and one out is best.

If your case is on the floor, you don't want fans on the bottom blowing in (because of dust/hair).

Regardless, I'd have two on top blowing in, and two on the bottom blowing out. You definitely want a fan near the video card doing something, as it's doubtless the largest source of heat in your case, and having that air immediately removed (and in a direction that discourages dust from entering your case) seems ideal.

That was actually my first choice with fan positioning. The thing I was worried about was the graphics card fan and the exhaust (case) fan are blowing in different directions, away from each other. Would that be detrimental to anything? My graphics card is a Direct CU II, the non-blower kind that releases the heat into the case. Regardless, I'd like the idea of having an exhaust as close as possible to the graphics card. Just need to know that there's nothing wrong with the setup.

What about one intake on top and two exhausts at the bottom? Or one exhaust on top and two intakes at the bottom? Or two exhausts on top and one intake at the bottom?

Or would it simply not make enough of a difference for me to actually debate this?

 

[Yuriman]

I'd do 2 in, 2 out, but most orientations should be roughly equivalent, so long as you're actually moving enough air through the case. I doubt fan direction near the video card will have more than a 1-2c effect.