Side Case Fan Duct

[K808]

im not sure if this has been done yet or not, but i was just thinking........for optimal cpu cooling, you add a side case fan and a duct that leads directly to the heatsink fan. Make it a tight fit somehow so that only the cool outside air is drawn in.

[Thelemac]

I've heard good things from people that do this...

[plague]

I'm about to do this, the only thing you said that is different though is to make it a tight fit on the hsf. Everyone that has done this says to leave about a 1 inch gap between the end of the duct and the hsf for maximum airflow. I would do it this way, as others have obviously learned this works best.

[chaosdriven]

Until I got my Alpha I was cooling the system with just a ducted Sunon 120 blowing directly on an SK6. It worked pretty well but the total airflow was quite reduced. Max stable OC was 1596.

When I got the Alpha I basically got lazy and decided that I needed to stop playing around with it because I needed it at work.

So right now I have the same 120 Sunon, side case mounted blowing onto the cpu and motherboard. The Alpha has a 68cfm Delta. Now this is all rather loud on full voltage, but I have both fans operating on the same variable voltage circuit.

It's 100% stable at 1660, CPU temp@44C, CPU fan rpm@2678. And reasonably quiet. :D (the room is fairly cool..) All air!

[plague]

chaos thats incredible... 1660 with air. wish I had a chip that good, but I'm stuck with an AXIA "9". Do you have your side panel fan ducted, or just blowing in?? I'm gonna make a duct soon and hopefully break 1.5..........

[nihili]

Originally posted by plague
I'm about to do this, the only thing you said that is different though is to make it a tight fit on the hsf. Everyone that has done this says to leave about a 1 inch gap between the end of the duct and the hsf for maximum airflow. I would do it this way, as others have obviously learned this works best.

Where did you see this? I've seen recommendations to leave a gap between the [I]fan{/I] and the heat sink, but not the duct.

The gap after the fan allows the air to fill in the natural dead spot that occurs at the center of the fan so you get a more even flow, this in turn decreases the turbulence, which results in reduction in static pressure and noise. A decrease in static pressure in turn means your fan pushes more air over the sink. Unless you've got a thermoengine, you should definitely have a gap between the hs and the fan.

The duct, however, should fit tightly against the hs. This makes sure that all the air from the duct flows past the fins of the hs. If you leave a gap, then much of your airflow will be shunted out the gap rather than flowing across the fins where it can do some good.

nihili

[spooge]

i tried a side duct this way.

drilled 2" hole on side of case, and mounted tube directly onto
hsf. i left 1/2 space from the tube to the side of the case. the 1/2"
gap was takin up with a seal. this wa i have Only outside air comming in. i'm running @ 1500 39c/44c.

[plague]

Originally posted by nihili


Where did you see this? I've seen recommendations to leave a gap between the [I]fan{/I] and the heat sink, but not the duct.



http://www.overclockers.com/tips586

the only difference here is that he put a sink w/o a fan on the cpu, I think I'll leave my fan on

[JaY_III]

ADDA 120 is the best fan for making a blowhole/duct.
108CFM.
Did this for my buddy, his athlon 1266 does 45C underfull load. (FOP heatsink)
was running around 50-55 before.

[nihili]

Originally posted by plague


http://www.overclockers.com/tips586

the only difference here is that he put a sink w/o a fan on the cpu, I think I'll leave my fan on

I'd like to point out that despite the fact that he draws this conclusion, he does so on the basis of no evidence. He makes the hypothesis, declares it as true, but never tests it.

Distancing the duct from the heat sink will in fact increase the airflow through the duct - you'll get more overall air into the case. However, you'll get less air across the heat sink as the air now has an easier path to follow.

If the purpose of the duct is to provide airflow across the sink, you'll do better to not leave a gap. Notice that many manufacturers actually include a shroud on their heat sinks which both distances the fan and ensures that the entire airflow passes over the sink.

Furthermore, since you plan to leave the heat sink fan on also, if you make the duct tight against the heat sink fan you'll also benefit from an increase in RPM of both fans. This should go some way toward mitigating the airflow lost to the increased static pressure.

nihili

[BobbyEwing]

What I did was using a flexible ventilation hosing, remove the delta from the sk6, and put the duct snuck on the sk6. The air is moved from the room using a 105cfm 120mm fan in the side.

All fans (the 120mm side, the front intekae and the rear + top exhaust) are switchable between 7 and 12 v.

When running all fans full power, I get a full load temp of about 41C. This at a much reduced noise then with the delta.

Lowering the speeds, wich is usable for web surfing, word processing etc, the fan noise is reduced to a wisper.

I tried the duct using a couple of different methods.

Tried a duct, and leaving the fan on: this did nothing to reduce cpu temp.
Removed the HSF and let the duct expell air an inch from the HS: This again did not improve temps, but it did reduce noise.
And finally my version: This improved full load from 45c to 41c, AND it reduced noise.

All with a 1200@1410