A question of fans

[shppr01]

I have a quick question on fans.
 When having two fans in the case(one in front , the other in back), Is it better to have one intake fan,blowing into the case to cool and one exhaust. OR would they both need to be exhaust ? How would you set them up?
 Just asking ! 
Thanks for any input..
 

[DubiousKB]

IMO -

It is better to have a balanced intake and exhaust arrangement. This will ensure that the fans aren't working to pressurize the tower, but equally drawing air in as well as removing warm air.



Ideally, your intake fan should be at the bottom of your case as to ensure the coolest intake air. (if you're ever worked at height on lighting or other cable runs, you'll know how much hotter it can get within a 2 foot distance, HOT AIR RISES). Furthermore, ensure that your exhaust fan is at the rear and top of the enclosure, this will ensure that the hottest air is removed from the case and directed away from the intake location. You don't want to recycle already warmed air back into the thermal management system.

If anything, I would have more intake air than exhaust, at least that way the enclosure has positive air pressure and is less likely to draw in debris, dust, hair, etc. ... But this just a personal preference as I have animals in the house... 

Ideally, balance your intake and exhaust, and ensure optimal air flow over your devices (CPU, video card, RAM).... 

  Hope this helps!

-KB

[Bizman]

That's a classic picture, Dub! Good find. I agree that intake should be in the bottom and exhaust on top, just as you said based on how hot air rises. What I disagree with is pressurizing the case although you have a point with the animal hair. I've heard someone even turned the airflow direction to the opposite of your picture for reducing hairflow!

So I'd recommend more exhaust than intake. IMO the intake fans mostly serve for directing the cool intake air to certain hot spots like under the video card. Too much negative pressure isn't good either, it will fill every gap with dust - even the optical player. As Dubious said, balanced intake and exhaust is ideal. A case with a mesh in the front will let enough air in without choking even with multiple large exhaust fans. For hair and other debris easily cleanable filters are a better alternative than trying to move air against the natural thermodynamic direction. A CPU stand or something else like a stool or a couple of bricks lifting the case a few inches off the floor will also radically decrease the amount of intake dust and dirt. Solid floor like wood, vinyl or stone is much better than a carpet; no matter what the floor is made of, vacuum cleaning will also help a lot.

As you see, the basics are very simple and inexpensive.

Yet another fact about fans: If you're concerned about noise, several large slowly rotating (<1000 rpm) fans will move more air with much less noise than one small whirling at 5000 rpm.