Homemade CPU Duct

cessna152

Golden Member
Feb 10, 2002
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I have a dual xeon system. The stock 60mm fans are ridiculously loud. So I decided to build/fabricate something very similar to the Dell Systems. I have a duct that guides the air coming from two 80mm fans onto the heatsinks. Will this work/is it safe?

Pics:
Pic 1
Pic 2

The duct is constructed of stiff cardstock. Air is sucked in by the 80mm case fans. Its guided to blow over the heatsinks thru the holes where the 60mm fans used to be.

Feedback would be greatly appreciated :)
 

Navid

Diamond Member
Jul 26, 2004
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The standard air flow direction in a case is for the cold air to enter the case from the front bottom and for the warm air to exit from the rear top. It makes sense since warm air is lighter than cold air.

You are forcing air to enter the case from the rear top!

There are a few things I can see that can not be to your advantage.

Your power supply fan sends warm air out of the back.
Some of the air sucked in by your fans are going to be that same warm air from the power supply. That reduces the efficiency of your cooling system.

Forcing air to move in from the top, you force air to move out of all the other holes including the bottom. But, the air at the bottom is cold (heavier). You should not force cold air out of the case.
 

xbassman

Golden Member
Feb 25, 2001
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My son has a Fong Kai FK-320. It uses a duck like in the pics.
Drawing air in through the duct with a Panaflo H1A 90mm temps dropped about 5C.

Here's a pic for reference Fong Kai duct

I wound up cutting 2 80 mm blow holes high on the door for exhaust, since it made no since to reverse the 120mm intake (lower front)

That said, doing this won't quiet your system like a Dell. You will still need your loud 60mm fans to cool your heatsinks. Dell make their own shrouds that cover the heatsink and draw out the hot air using only a 92mm fan with none on the heatsink.

A better solution would be to replace your heatsink/fan combo with a quieter/more efficient unit.
 

cessna152

Golden Member
Feb 10, 2002
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The case is a rackmount actually. And I just reversed the airflow in the case. So the top is actually the top in the picture. :p
 

pelikan

Diamond Member
Dec 28, 2002
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Ducts work great for cpu temps. People get between 5-10C lower temps with them.
I've seen people put a little flap under the psu that deflects the warm exhaust upward, away from the duct intake.
 

lenjack

Platinum Member
Oct 10, 1999
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The Dell duct works because it uses a large rear fan to exhaust air from the heatsink. In fact with the Dell duct, there is no fan on the heatsink.
 
Aug 27, 2002
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Originally posted by: lenjack
The Dell duct works because it uses a large rear fan to exhaust air from the heatsink. In fact with the Dell duct, there is no fan on the heatsink.
yep, but one thing to note, thier 2.8Ghz and up systems have heat issues in warm rooms (80F ambient), or systems that actually get taxed by gamers/DC'ers.
 

Zepper

Elite Member
May 1, 2001
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You will have a back-pressure problem - the tops of the fins of the heatsinks will look almost like solid walls to air coming from those remote fans - it will try to go anywhere but down into the fins, as air (like water, electricity and students) takes the path of least resistance. But give it a try and see what happens. If it doesn't work well, I would get a pair of 60x60x25 high quality fans and run them off speed controlers to cut the noise down to an acceptable level.
.bh.
 

0roo0roo

No Lifer
Sep 21, 2002
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do not use flamable materials in your case.

it will work if you put a deflector on your psu output. not sure its really necessary if you have a decent case flow