Airflow within a positive pressure SFF case: turbulence vs effective air volume

griff1

Honorable
Mar 21, 2013
18
0
10,510
0
Hello,

I am building a SFF gaming rig and now the main components are in the post I was puzzling about some of the final touches on case airflow.

Please see this photo: http://i1143.photobucket.com/albums/n634/Idarzoid/PC%20stuff/SG05%20build%20log/IMG_0420.jpg

The gent who uploaded these pics has the same thermal setup as me - CPU cooler model, position, and blower style GFX card wise. (more pics: http://forums.overclockers.co.uk/showthread.php?p=23806413 ) edit I just noticed he has flipped his PSU so it intakes from the top exterior. I'm concerned about hot air getting stuck high in the case with no way out, plus the inside of the PSU getting dusty if I did this

The SG05 is a positive pressure case - provided by a single unrestricted 120mm intake. Whilst the CPU cooler blows down and the PSU exhausts up from ~ 30mm above it, they do not starve each other: the CPU cooler causes turbulence down onto and around the mobo components, with the hot air then rising up and being exhausted by the PSU - no air is actually being ducted out of the case by the CPU cooler, so the effective air volume within the case remains the same.

The question: If I was to replace the mobo i/o backplate with modders mesh (or just remove it all together) to provide a 'ground level’ exhaust route for the hot downwash from the CPU cooler (AXP-100), would this reduce the effective air volume within the case to the extent that the PSU intake was fighting for airflow? Does an unrestricted 120mm intake fan provide a high enough volume that this is not a concern?

From this pic ( http://content.hwigroup.net/images/products/xl/060788/2/silverstone_sugo_sg05_black_300w.jpg ) you can see there is already an exhaust route on the opposite side to the GFX card, but the manufacturers do not extend it down to where CPU cooler downwash could have a direct exhaust flow. Is this an indication they were concerned this?

So why am I going to all this trouble? I cannot easily replace the SFX PSU's fan with a quieter model, and I was hoping I could get some of the CPU, RAM, and mobo heat out via a different route so the PSU fan didn't have to work as hard to cool the actual PSU - especially considering the load the PSU will be under.

I am trying to reduce noise - so just putting an extremely powerful 120mm intake fan in isn't the answer!

Thank you for any help you can provide.

All the Best,

Griff
 

c_for

Distinguished
Oct 13, 2010
129
0
18,710
6
I used to have a HTPC in a SFF case with a similar setup and I found that I originally had the same problem. The PSU and CPU fan were fighting against each other for airflow causing turbulance noise. My solution worked well for my setup but it lowers the cooling power of your CPU so depending on your hardware this may not work for you.

My PSU was situated directly over the CPU heatsync/fan. I was using the stock intel heatsync. I removed the fan from the heatsync and used a short piece of PVC pipe(about 2" long) to direct airflow around the CPU heatsync and into the PSU. So air was essentially routed over the heatsync fans and pulled through the PVC pipe through the PSU and out through the PSU's exhaust. I secured the pipe using cable ties and an small pieces of rubber as a decoupler to reduce noise.

When I first did this setup I found I wasn't getting enough cooling power. I then opened up my PSU and swapped the fan with a higher quality one and that further reduced the noise and made the cooling sufficient.

I recommend running this through a stress test before relying on it as a gaming pc though as this solution may not provide enough cooling power for your setup. Also if your computer looks like his you need to do some serious cable routing work. Better cabling will increase cooling ability. The better the cooling ability the slower the fans can run which will also reduce the turbulence noise that you are hearing.
 

griff1

Honorable
Mar 21, 2013
18
0
10,510
0
I've just spent a bit of time reading up on fan swaps within the PSU. The model that comes with my case has the old fan connector soldered onto the PSU beneath silicone. I don't have a soldering iron, so can you foresee disaster if I strip the wires back, retwist, and electrical tape them?
 

c_for

Distinguished
Oct 13, 2010
129
0
18,710
6
Personally I would not do that. PSU's are dangerous to work in if you don't know what you are doing. I felt comfortable swapping mine since it was just unplugging the fan from PSU's. If you feel your electronics knowledge is high enough then go ahead... but do be careful.
 

ASK THE COMMUNITY