Push/pull fan question

[kruzn4evr]

Ok, here's the thing, I'm installing a 320 rad in the top of a HAF 932 and will be cooling the cpu only and I'm trying to decide which direction the fans should go. Should I be pulling air in which would then bring in fresh air to cool the rad or should I push air out from the case. My way of thinking is pulling (intake) air in would be better because it would then create more down air flow and would help cool the 2 GTX 295's. On the other hand, pushing air out would help remove the warmer air the GPU's give off but would then be pushing (exhaust) warmer air through the rad. Seems to me pulling cooler outside air makes more sense.

What say you the jury???

[sswilson]

My way of thinking is just the opposite WRT airflow within the case.

Hot air tends to rise which is why "blowhole" fans on the top of a case are an effective method of reducing overall system temps.

Your vid cards & motherboard components are the main culprits when it comes to heating up the air inside your case. If you start blowing air down from the top you're effectively pushing that hot air back down onto the components that are producing it and thus need to get rid of it.

[Sagath]

+1 to Wilson. I've always been a fan of exhausting cases with a negative pressure. If the majority of your fans are blowing air out, fresh air will find a way in. Physics (I think) are your friend!

[misterlarry]

I think it really depends on the individual configuration and air flow of the case. While the set-up that you suggest sounds like it should provide the best solution, there is another way to look at it.

By pulling air past your rad into the case you will be introducing warmer than ambient temp air and also trying to force hot air (off of GPUs) downwards. A case can be made for trying to expell that hot rising air as quickly as possible and laterally pulling cooler ambient air into and across your GPUs.

Unfortunately, I believe that there's only one way to get a difinitive answer in your situation, and that is to try both ways under similar conditions. I know that I'm not much help kruzn. But if you do try the experiment, I would be interested in the results.

[ChuckleBrother]

Setting it as an exhaust is better overall imo because you only sacrifice a few degrees on the CPU rather than heat of the whole case. Because you really will mess up the whole case temp if you do intake up top. I tried for a while with a Q6600/8800 in a loop with a PA120.3 and an swifty 220(this was the rad blowing in) and it was causing instabilities and crashes. My ram went from warm to the touch to hot enough to burn. The whole top of the case(being aluminum) was also warm-hot to the touch because of trapped air.

Now this is only my experience and my not mirror yours but I really do not recommend it based on what I have seen happen.

[gingerbee]

have my 320 rad in the top of my haf with 3 yate loons blowing out the top this coos my i7 and 4870 and works great ( would give pics but crappy cam only blackberry blod)
1+ to sswilson heat rises so use thermal dynamics to your advantage

[kruzn4evr]

Somehow I thought I might get mixed opinions on this...lol...so here's another thought, what if I set the big 230mm side panel fan as the exhaust fan? that would suck out the hot air from the gpu's as cool air is pushed in from the top, also the 140mm rear exhaust along with the 230mm front fan would create a cross flow would it not? Oh yeah, I may have room to mount a fan on the bottom of the case to exhaust the gpu's fan flow as well, I haven't looked at that yet but I think it would help.

[ChuckleBrother]

Likely would, an option is to set the rear fan as exhaust and a high speed to try and remove as much of the hot air from the top radiator as possible. It won't be hard to counteract the issues it would cause, but it definitely will not be as quiet as setting the top rad as an exhaust.

A decent fan in a bay device would also help if you have one(my solution to my crazy hot case-top).

[gingerbee]

positive case pressure is what you want. unless you have your case upside down. hot air rises you will be fight the natural way the heated air wants to go. that being said it's your computer ? you can do what you want the only fans that exhaust air in my case are the ones that blow out the top through the rad.

[Dazmode]

Originally Posted by ChuckleBrother

... swifty 220(this was the rad blowing in) and it was causing instabilities and crashes. My ram went from warm to the touch to hot enough to burn. The whole top of the case(being aluminum) was also warm-hot to the touch because of trapped air.

You probably didn't have enough exhaust fans or if hot air came out your rad - you had too much parts on for your rads size.