When mounting extra case fans...

[metallibloke]

...is it best to have them suck cool air in from outside, or blow hot air out?

 

[DougK62]

It depends on where you mount them and how you want to setup the flow in your case. Typically fans put on the front or bottom of the case bring air in and fans on the back and top blow air out.

 

[metallibloke]

Thanks for the info!

 

[kly1222]

The best way to do it is to make sure you have the same amount of airflow coming in and going out.

 

[jamautosound]

The best way to do it is to make sure you have the same amount of airflow coming in and going out.

kly 1222, how do you accomplish this. Do I have to know each of my fans cfm? Thanks.

 

[CarpetMan]

Won't the ventilation slits in the side (or back)of the case equalize the pressure inside?

 

[mstudd]

Having roughly equal CFM going in and out is a good idea, but I tend to think more incoming air is slightly better. If you have bigger fans sucking the air out, the cold incoming air will travel straight to the exhaust fans, not filling the case with cool air.
If your inlet fans slightly pressurise the case, the cooler air will fill the case better.
This is my theory and I take it from the theories of volumetric efficiency that are used in designing automotive engines.
I may be wrong, but I would like to hear any other opinions on the subject.

 

[Chudilo]

Bzzzzzzzzzzzzz , Wrong. Filling The case with air is a bad IDEA !!
The whole point of cooling is you're trying to EXTRACT heat from the CPU not surround it with cool air and keep it there. Cause it'll get hot eventually. Thus Exracting HEAT / air is the KEY, all the gaps and cracks and air holes in the case are plenty as intakes for the air.

The heatsink Extracts heat from the CPU thus the more air you get away from the heatsink the better, blowing wind on the heatsink would work but only in an open air situation. In a closed case you're just heating as much air as possible, which is the opposite to what you're really need to be doing.

Although if you're gonna mount the third fan away from the CPU then I'd set it on intake.

Bottom line The Fans that are close to CPU should be sucking air away from it and sending it outside.. The optional case fan up front should probably suck the air in.

Proved by trial and error and research.

 

[Darkluck]

I'd agree with Chudilo. I've set my case up mostly with this idea in mind I have one fan sucking in at the bottom and two expelling heat/air at the top. I've been running my rig with the case off this last week cuz I am waiting for my swiftech to arrive (been using the stock amd fan that came with the cpu). If you want I can post results for ambient temps with the case on and off. Let me know if this interests you.

 

[frankroh]

I've heard people flipping their cpu fan upside down so the fan is moving the air away from the heatsink, which reduced their cpu temp.

If anyone has tried this and think it is a valid exercise, please disclose.

 

[LongTimePCUser]

Chudio is wrong because the power supplies push air out of the system.
You have to check on the proximity of the power supply vents to the cpu. If it is a small case then the power supply vent may be just next to the cpu. In that case you want to reverse the cpu fan to match the direction of air flow from the power supply.

Since the power supply is trying to push air out of the system you have to make sure that enough air is coming into the system. That is why you need a fan pulling air into the front side of the tower.