Airflow in case - feedback welcome

girlscoutdk · Post by **girlscoutdk** » Sat Sep 19, 2009 9:43 am

I'm currently working on a custom enclosure (width: 600mm, height: 800mm, depth: 180mm) for wall mounting and in the process of figuring out the correct position for the fans.

It's not a silent PC per se (seeing as it has two Laing D5 vario pumps and a LOT of fans), but I do plan to undervolt the fans and hopefully get as good a CFM to noise ratio as possible.

Anyway, the current layout can be seen here: http://www.gratiaplacendi.dk/case.jpg (http://bit.ly/nHJT6).

The dotted lines denote fans. The round 230mm fans are mounted on the top, while the 6 120mm fans cooling the radiator are mounted on the bottom. The round 230mm fans are pulling air from outside the case and the radiator fans are setup in a pull scenario, pulling air from inside the case and out on the backside (which will be the side its mounted on the wall with a 10-20mm distance to the wall.

I've done some studying on the effect on pull vs. push scenarios for the radiator cooling and it doesn't seem to make much of a difference, so the pull-idea isn't something I'm married to. Anyway, I'd much appreciate any feedback, so shoot away :-9

ascl · Post by **ascl** » Sun Sep 20, 2009 12:01 am

Push vs Pull can make a decent difference (10% ish depending on the fans):
http://martin.skinneelabs.com/Radiator- ... eview.html

The rule of thumb is pull for < 1500 rpm and push for above that... with a grey area in between where it doesn't make much difference at all. If you have the room, shrouds will make a decent difference in fan performance AND make the fans a little quieter.

Regarding the airflow of the case... it seems confused. Do you really need all those fans? That said... its very difficult to predict was is going to be the best solution. I had a situation once where increasing an intake fan speed increased my CPU temp! So, test it, see what works for you.

Hope that helps!

EDIT: Have you got a photo? Might make it easier to see if there is something obvious you can improve?

girlscoutdk · Post by **girlscoutdk** » Sun Sep 20, 2009 7:36 am

ascl wrote:Push vs Pull can make a decent difference (10% ish depending on the fans):
http://martin.skinneelabs.com/Radiator- ... eview.html

The rule of thumb is pull for < 1500 rpm and push for above that... with a grey area in between where it doesn't make much difference at all. If you have the room, shrouds will make a decent difference in fan performance AND make the fans a little quieter.

I'll most likely be running at less than 1500 most of the time, but there is a twist. One factor is the fans below the radiator (2 x 3 120mm fans) pulling air out, but another is the two 200mm fans (antec big boys) pushing air at the radiator at the same time. I'm fairly sure the pull vs push wont make a big difference in that regard, but when I'm done with the setup I can simply try both and see which works better, so it should be fine

Regarding the airflow of the case... it seems confused. Do you really need all those fans? That said... its very difficult to predict was is going to be the best solution. I had a situation once where increasing an intake fan speed increased my CPU temp! So, test it, see what works for you.

The general idea is to pull air in on the bottom of the case and push it out through the top. Due to the radiators in the middle, it probably is a bit confused.

My best guess would be no, I don't need all of the fans - especially since most of the components will be water-cooled (not sure which way I'm going with RAM just yet), but CPU, GFX and chipset for sure.

Regardless, I'm not sure which fans to take out. I may not need the two "southern" fans on the bottom for intake, since I have the three big-boys already.

EDIT: Have you got a photo? Might make it easier to see if there is something obvious you can improve?

Unfortunately no - I'm still doing some of the metalwork on the case, so it's not final just yet, but I'm working on it

ascl · Post by **ascl** » Sun Sep 20, 2009 5:30 pm

Sounds like a good plan (air in at the bottom, out at the top). Works with heat rising. You may find however, that you don't need many fans sucking air in, definitely something to try out.

Another thing, the bigboy fans quite likely have low static pressure, and may not actually help much against a radiator. It will probably work better with some quality 120mm fans (and may be quieter). I could be wrong here, not sure anyone has actually tested them, it just seems unlikely given their design.