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Best air flow for case?

Positive or Nagetive air pressure?

  • Positive

    Votes: 6 66.7%

  • Nagetive

    Votes: 3 33.3%
  • Total voters
    9
P

Proxy

Pumpkin Ghost
Joined
Apr 24, 2005
Messages
4,308
I was wondering what would aid cooling better, positive or negative air pressure? I know I have heard a lot of people talk about how negative air pressure is better, but it can attract lots of dust bunnies. I don't mind that so much since I clean my case out so often. I currently own a 650D and was trying to figure out how to get the best possible cooling out of it.
 
In my experience I've found that equal force is best, but if you have to bias one way or the other slight negative is the way to go.
 
a) Correct your spelling of Negative
b) It's been shown to be positive over and over
 
My general impression is that it depends on the case and on the fans you have in there. There is in the internet a link with a test with a case with many fans (over 5), in which they tried all combos and came up that only 1 rear fan is the best. So negative pressure. The explanation was that many fans at the end tend to interfere with each others' flow and they ruin the main front-rear flow. I can't find the link right now, but i 've stumbled upon it several times in the past while googling.

In this one, for CPU, seems neutral is best:

http://www.hardwaresecrets.com/printpage/Which-is-the-Best-Place-to-Install-a-Case-Fan-Part-2/1483

In my own case, it's positive pressure. I have a fan controller, so i 've done this test many times. I 've got 4 fans installed, all 120mm and approx the same speed. 1 front 1200rpm, 1 rear 1000rpm, 1 upper side 700rpm, 1 lower side 1000rpm (reinforced with Nexus BeamAir). Only the rear is exhaust. My case also has a top grill, but it's without fan and mostly covered.

Done again today (where we 've got a sudden rise in ambient temperature).

Only rear = Front and rear = CPU 52C, motherboard 37C
All fans = CPU 50C, motherboard 33C.

Which doesn't come as a surprise, since according to the manufacturer, my case is supposed to be designed for positive pressure:
http://imageshack.us/photo/my-images/545/45267112.jpg/

So i vote positive. But seen how others have much less difference or inverted results, i 'd say it's case and components dependent. For example, my VGA has passive cooling. If it had a fan, the airflow would be affected. Also, my PSU fan is faced downwards on the bottom of the case. If it was upwards or top mounted, airflow would be different and this would affect the general airflow. Same for ventilation holes, etc.

So, try and see what works in your case.
 
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