Lets talk about air flow

eyetrip · 11 May 2012 at 14:03

Well, too tired to be much good at coding today, so my mind is wandering and I got to thinking about airflow in my case, probably after a thread the other day asking about side fan as intake/exhaust.

Read the following:
More recent study: bit-tech study

Much older study from 2003

:
http://icrontic.com/article/pc_airflow_heat_cooling_guide

Now, my case has the option for many fans, and I imagine for the most part it's in line with most cases available now.

2x120mm front, 1x140mm bottom, 1x140mm side, 2x140mm top, 1x120mm rear. Now I am sure there will be variations on this from large 20cm intakes etc, to 4 x side fan mounts, but I think the general air flow principles will remain the same.

Now would I be best off just populating as many as I could such as
Front: 2x120mm intake
Bottom: 140mm intake
Side: 1x140mm intake
top: 2x140mm exhaust
Rear: 1x120mm exhaust

I can't help but wonder how all this works together in the larger picture...

Am I actually messing up airflow with all these fans? Probably, and once I got my new cooler installed I might spend a little while trying different things.

I know the side intake definitely helps with keeping the GPU's cooler, and setting as exhaust temps shot up, but I never did look at rest of system - was suggested doing so would lower board temps.

I am not looking for anyone to advise me on which way to go here, but I am keen to hear peoples experience form trying different things, and what worked and what didn't.

varkanoid · 11 May 2012 at 16:37

in at the front, bottom and side out at the back and top.

(only other advice is just use one rear top 140mm instead of two)

Simple.

craarc · 11 May 2012 at 16:47

in the past i have found

bigger fan the better as in 1 x 240mm generally is better than 4 x 120

and general rules applying to heat rising and positive case presurre worked for me

eyetrip · 11 May 2012 at 16:54

Yes, I was recently using two at top, and from reading that bit-tech article, sound like that might not have been a good idea.

Keep thinking all my recent woes with temps have been down to how I have my fans.

And can using high speed fans sometime be more detrimental than using normal speed fans?

E.g. if I only had a fan in bottom, and not side, to blow over two gpu's in crossfire, if I had the fan speed too high, could the air be blowing too fast for the top card to get a chance to suck in any air? Not sure I explained that well, but hopefully you get the it.

You know like if it's a windy day, you move around a corner, and the wind doesn't reach you because of the wall? Though I suppose a gentle breeze would suffer the same...

Mal X · 11 May 2012 at 16:58

sort of like that i think, but i'm not sure about the fan power, i might replace the Xigs with those Megahalems fans instead, the cooler is fine, it's the two intakes i'm not sure about

Mal X · 11 May 2012 at 17:04

eyetrip said:
Yes, I was recently using two at top, and from reading that bit-tech article, sound like that might not have been a good idea.

Keep thinking all my recent woes with temps have been down to how I have my fans.

And can using high speed fans sometime be more detrimental than using normal speed fans?

E.g. if I only had a fan in bottom, and not side, to blow over two gpu's in crossfire, if I had the fan speed too high, could the air be blowing too fast for the top card to get a chance to suck in any air? Not sure I explained that well, but hopefully you get the it.

You know like if it's a windy day, you move around a corner, and the wind doesn't reach you because of the wall? Though I suppose a gentle breeze would suffer the same...

yes maybe, also it could be causing eddies and dead zones and areas of high/ low pressure..... my house always ventilates best if i open the front and back door, these tests are ok, but nobody has really ever investigated this well..... SLI is a big problem because the gap between the two cards is so small, especially for the card above

it's even hard to choose a good fan !

PapaLazaru · 11 May 2012 at 17:06

varkanoid said:
in at the front, bottom and side out at the back and top.

(only other advice is just use one rear top 140mm instead of two)

Simple.

There is truth in this as I currently have 2 x 140mm sucking air out of the top and I swear it is interfering with the airflow going into the cpu cooler as it is right above it. Both pulling in different directions.

Think I will hoik it out and fit it to the bottom to draw more air in as I am also now faced with negative pressure and my case has become a dust magnet.

doyll · 11 May 2012 at 18:01

I'm using a Define R2 with 2x 120mm in front & 1x 140mm bottom intakes. 1x120mm back exhaust with 2x 140mm on Noctua NH-U12P ducting out top. 120mm back exhaust is to keep air moving over mobo.

I'm a believer in keeping cool air separated from warm air and creating a current/flow of air through case. Problem is most component cooling is not conducive to keeping cool and hot separated.

Cool and very quiet.

j.col · 11 May 2012 at 20:52

PapaLazaru said:
There is truth in this as I currently have 2 x 140mm sucking air out of the top and I swear it is interfering with the airflow going into the cpu cooler as it is right above it. Both pulling in different directions.

Think I will hoik it out and fit it to the bottom to draw more air in as I am also now faced with negative pressure and my case has become a dust magnet.

here is a pic, from a guy on overclock.net, he is very well respected in their air cooling forum. (Ehulme)
have a read of this thread, or click a link in his sig.
http://www.overclock.net/t/1041926/how-to-decide-on-a-case-for-air-cooling-warning-pics

try how he has the top fans done

PiKe · 11 May 2012 at 20:58

I've always thought you needed positive air pressure to avoid sucking dust through the cracks in your case where panels meet up.

varkanoid · 11 May 2012 at 22:33

i think thats the sign of a poorly designed ill fitting case !

a neighbour of my Dad's had bought a new PC as his Mesh one had stopped working. It would not boot and got stuck on the POST screen. (it was so heavy I had trouble lifting it).

Took it apart last weekend and I could not see the motherboard for dust. No joke, not one component could I see. It was like some kind of disaster movie where "volcanic ash" was steeped up the size of the RAM, CPU cooler etc.

A lot of people buy a PC and do not clean them out regularly (okay prob not people who frequent boards like this !)