Push or pull?

[Cogman]

Hello, I'm starting a new build, I ordered 2 120mm Fans, one rated at 80 CFM and the other at 68. The tower is going to be situated close to the back of the case so I was wondering if I should put the stronger fan on exhaust or CPU cooling?

I have a Cooler Master Centurion case (I believe) and it stays pretty cool as is. My thinking is if I put the stronger fan on the exhaust that it will still cause some suction on the heatsink plus pull out more of the heat (leaving less trapped).

 

[f4phantom2500]

if all you have is the 2 120's and the psu fan, i would put the weaker 120 in the back of the case for exhaust and the stronger one in the front for intake. since the exhaust one has the additional help of the power supply it doesn't need to be as strong (besides 68 is still a lot of air), and the stronger air flow will be better suited for the front since it has to first cool the hard drive(s) and then the rest of the computer. you want to keep the intake and exhaust pressures created by all of the fans as neutral as possible, which is why i suggested what i did.

 

[Jeff7181]

I usually like more intake than exhaust... otherwise in the process of exhausting more air than your intake fans can bring in, you'll suck air and dust in all the little seams in the case making it more difficult to control the dust that enters the case.

 

[funboy6942]

I have mine set up so the front one pulls in, and the back one draws out. That way the air coming in gets drawn out across the mem and cpu and pulls and heat out with it.
And of course the PSU has a 120mm fan as well, so it draws more air through the front across my hdd's.

 

[Cogman]

I remember reading once that a even pressure was Ideal, negative second best, and positive the worst in cooling, is this still true?

Also, The heatsink is a tower (Thermalright ultra 120) Im thinking that I want to have a negitive pressure between the heatsink and the back of the case (put the stronger fan on the exhaust and the weaker one on the heatsink) That way the stronger fan should pull more air from the heatsink. That is my current thinking (I don't think this came through my post)

BTW noticed this was on the CPU forum, I meant to put it in the cooling forum (slip of the click) Sorry about that.

 

[Jeff7181]

Originally posted by: Cogman
I remember reading once that a even pressure was Ideal, negative second best, and positive the worst in cooling, is this still true?

Also, The heatsink is a tower (Thermalright ultra 120) Im thinking that I want to have a negitive pressure between the heatsink and the back of the case (put the stronger fan on the exhaust and the weaker one on the heatsink) That way the stronger fan should pull more air from the heatsink. That is my current thinking (I don't think this came through my post)

BTW noticed this was on the CPU forum, I meant to put it in the cooling forum (slip of the click) Sorry about that.

Yeah, physics hasn't changed. Positive pressure (like I suggested) will create more dead zones. Temps aren't a problem for me so I don't mind, and the dust control is worth a degree or two in my opinion anyway.

 

[myocardia]

Originally posted by: Cogman
I remember reading once that a even pressure was Ideal, negative second best, and positive the worst in cooling, is this still true?

Also, The heatsink is a tower (Thermalright ultra 120) Im thinking that I want to have a negitive pressure between the heatsink and the back of the case (put the stronger fan on the exhaust and the weaker one on the heatsink) That way the stronger fan should pull more air from the heatsink. That is my current thinking (I don't think this came through my post)

You'd be much better off with a dedicated fan on the Ultra 120, and having the slower fan as an exhaust. You want to be as close to neutral on case airflow as possible, and since you have a psu with a single fan, that goes double. Back a few years ago, when all of the psu's had two fans, it was okay to have negative case pressure, since the psu (the most important part of your computer) had it's own intake fan and exhaust fans-- the pressure inside of the case didn't make much difference.

Now that nearly all psu's have only an intake fan, and nearly everyone has a side intake fan, they are relying on your case to have a slightly positive pressure. That will force some air through the psu, and carry it out the back. Just remember, if your psu starts to get warm, it no longer puts out the power that it's rated to be able to produce.