What's today's theory on positive or negative air pressure?

GilmourD

GilmourD

[H]F Junkie
Joined
Jun 17, 2004
Messages
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I've got a Chieftec Dragon case... Yeah, it's old. Don't laugh. I'm broke.

Anyhow, I need new fans and I'm trying to figure out which fans to get. It's got 80mm fans all around, two intakes up front on the bottom (one above the other), an intake on the door over the expansion slots, and two exhausts on the back below the PSU (one above the other).

So, do I want more intake and less exhaust or the other way around?

And I did search. If anybody asked this question they didn't word it in a way which matched up with my search.
 
PAo_ReVoLT said:
can you draw a layout of yours component please
Click to expand...

I'm on vacation, so I'm not actually at my computer nor do I have anything besides MS Paint on this laptop even if I did remember exactly what everything looked like. LOL

However, everything's in my sig and I have the black version of this case if it helps.
 
if you have them setup to pull air from the front to back its a good setup.. as long as you can keep a constant flow of cool air in the case you should be fine.. just keep the front ones pulling in air and the back ones removing the air..
 
sirmonkey1985 said:
if you have them setup to pull air from the front to back its a good setup.. as long as you can keep a constant flow of cool air in the case you should be fine.. just keep the front ones pulling in air and the back ones removing the air..
Click to expand...

Well, that's a bit more basic than I meant... LOL Thanks, though. That much I do understand.

Now that I'm back from vacation I can be a tiny bit more elaborate. Beyond just the basic direction of the flow, I wanted to know whether or not it's considered better to have positive air pressure in the case (more CFM on the intake fans than the exhaust) or negative pressure (more CFM for the exhaust than the intake).
 
I remember reading a discussion about this on these forums... It was honestly probably 6 or 7 years ago.

The general consensus was that it didn't really matter: Your computer case isn't air tight and you won't be changing the pressure too much in your case unless you get ridiculous with your fan setup.

However, people also said that it's generally better to stay on the low side: High pressure is bad for temperatures.
 
very high positive / negative = bad

negative = better cooling, prevents dead hot air areas in harder to reach areas.

positive = no dust in case. and through components.
 
I like positive pressure on mine - my thinking is that the exhaust fans might be pulling cool air out (depending on air flow) leaving some pockets of hot air in the case. With more intake than exhaust I am pushing more cool air into the case, which will eventually force the hot air out through the PCI slots or other air gaps. Never tested it to see if it works that way, but in my mind pushing more cool air in is better than trying to pull more hot air out.
 
Truthfully, as another has said it, there really isn't a big difference until you get into noticable extremes. Your rig could survive with all the fans being intake or all exhaust. It's only when you're using super high-CFM fans, or you're doing something definitely out of the ordinary that you'll start to see benefits from a certain type of air pressure.

One common thing with a lot of cases is that their makers seem to believe that mesh panels and vents means more airflow. Unfortunately, the REAL world of physics doesn't work this way. Get whatever fans you want, and try to mod the case so that the only way air can get into or out of your case is via your fans. Any vent of mesh panel will do nothing but short-circuit your airflow.
 
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