duct question

[mccompunerd]

okay guys, i'm getting ready to cut my side panel for a 120mm fan and was wondering something.. i'm at least going to be putting a fan directly over the cpu, and possibly one over the pci cards. would a duct from the cpu to the fan help my cpu temps? even if not, which way should it be blowing, into the case, or out? i have a chieftec case, with 2 fans blowing in on front bottom, and 2 blowing out just below the ps.. btw, this is for the rig in my signature, and right now(with the side panel off) the temps as reported by mbm5 are.. 33cpu and 30 case(ambient temp is ~23-24)
thanks in advance for the help :D:)

[felix88]

my CPU temps went up a little bit when i built a duct. i believe the duct just restricted airflow due to the design. anyway, my case temp did go down, which helped a bit.

i would suggest having the duct blow air in the same direction as your CPU fan. or you could just test the fan in both directions to see which is best.

good luck.

[Tweaked!]

You would want the air being pushed in towards the cpu, it's at its coldest point then. Otherwise you would be pulling the preheated air from inside the case through the heat sink, which would raise your temps a little. I doubt a duct would be of that much benefit, but as long as you maintain an even amount of intake and exhaust it should be good to go. I would set up the front lower fans as intake, as well as the side door panel fans, and have the rear fans exhausting. Another good place to locate a fan would be out the top, exhausting all the heat that rises to the top of the case.

[felix88]

true, but if the fan on the HSF is sucking air through it(like an Alpha) then a fan blowing air out of the case would be a better idea.

then again, it shouldn't be hard to try all the different combinations.

[mccompunerd]

thanks for the input guys, i'll have to wait 'til after i get the hole(s) cut in the side panel, then i'll prolly just use some cardboard or something to test out the different combinations.. i really want to put a fan up top as well, but the top panel of my case is riveted on, and i'd have to take the whole thing apart to cut it off, so that won't be happening for a while(maybe when i upgrade next round)...

[Teus]

http://www.madshrimps.be/articles/KoolancePC2-Cai-Teus-869.jpg
check it

Rear intake
I've placed a fan in the rear blowhole, and used it for sucking air into the case. Not a very common approach, but with some duck tape it made a great fan duct for my CPU cooling!


it lowered my temps with 4-5° :)

[JBELL]

I found fans blwoing in on side and sucking out at top and back the best.. I have pics of an old case of mine floating around.. if you do a duct - cover around fan but do not block esacping air around the heatsink... also runnign two fans can hurt you.. if you could find a fan running in oposite direction you will dramatically increase efficciency in it cuase of how it ''grabs'' the air... what case do you have? how many fans? what heatsink?

[mccompunerd]

if you could find a fan running in oposite direction you will dramatically increase efficciency in it cuase of how it ''grabs'' the air...

opposite direction of what?? my case is a chieftec mid-tower... i've got the 4 stock fans, 2 intake front bottom, two exhaust rear top, and am planning on having at least 1 either intake or exhaust on the side panel directly above the hsf... hsf is stock intel setup(for now)... here are pics from newegg of the inside...
http://willmccoy.home.attbi.com/case/case2.jpg
http://willmccoy.home.attbi.com/case/case3.jpg

4 fans front/rear are 80mm, fan(s) that i plan to stick on the side is 120..

[Teus]

let's explain it

| is housing
. is air
= is airflow

the CPU fan blows air onto your heatsink
|||....=====air==>HS

if the 120 sucks air away:
<===||....===>HS/fan
as you see, the fans are in opposite direction and this is completely useless: the majority of the air gets out of the housing through the 120 while a strongly reduced amount of air will reach the HS

if you add a 120mm fan, blowing on your CPU hs/fan you'll get this:
===>|||===>HS/fan
way better airflow: air from out of the case is directly blown on you HS giving sometimes a great performance boost!

[felix88]

well, not every fan is mounted to blow on the heatsink. i think the best idea is to keep the fans blowing in the same direction. so if the fan on the HSF is blowing onto it, have the duct fan blow onto the HSF as well. but if the fan on the HSF is sucking air away from the HSF, make sure the duct fan is sucking air out of the case.

just don't make the fans fight against each other.

i believe i understand what JBELL is talking about. like, a fan spinning clockwise, blowing air, and another fan spinning counterclockwise, but blowing air in the same direction.