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I have recently diyed a simple 120mm air duct which will act as an exhaust chimney. Simple, cheap, non time consuming and easy.
As I anticipate someone saying 'pics or it did not happen', I throw in a few pics to make this less 'boring' reading.
smile.gif


Basic components:- (see pics 1 and 2)
1. 120x38mm fan
Comment: this is positioned at the 'exit' end of the duct. This fan is necessary. If the duct is fully extended (~2 metre long) and/or oriented vertically like a chimney, air entering the duct will not have enough velocity to travel the whole length. The entering air needs to be drafted forward by an exhausting fan to get out of the 'exit' end of the duct.
A powerful fan with adjustable speed is recommended. I am using Delta AFB1212HE.

2. 120mm diameter plastic duct (extendable up to 2 meter long)
Comment: 140mm could be used but a powerful 140mm fan (for exhaust) is hard to be found. Alternatively, a 120x38 fan can be used in conjunction with a 120-to-140 converter to fit a 140mm diameter duct.

3. 120mm fan filter guard+retainer
Comment: provide structural support for the 2 ends of the duct. They also act as the coupling part for the fan at the exit end and for the entering end of the duct.
I cut away the grill portion of the filter guard and retainer and use the square frames for the purpose.

4. Fan controller
Comment: I have chosen a Zalman Fanmate controller. It is useful to adjust the speed of the fan to match the varying thermal needs. Running a 120x38 fan at full speed all the time can be noisy.

5. Extension cables
Comment: 4-pin Molex extension cables can be used when the fan is powered directly from the PSU. I have chosen to use 3-pin fan extension cables because I wish to monitor the rpm figure as well.

6. Fan shroud
Comment: this is primarily used to keep the blades of the exhausting fan from hitting the plastic duct. I have converted a 120x25 fan for this purpose. It is fixed the exhausting fan by four zip-ties.
 

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Discussion Starter #2
Final Product:- (see pic 1)
The most common usage is to connect the duct to a computer case's rear exhaust opening (pic 2). This helps if the case is positioned underneath a table or in an area with bad ventilation. Hot air expelled from the case will not accumulate at the rear but be directed to an area with better ventilation.
This duct can also be used to extract the case's hot air out of the room via a window opening.
(Note also that the duct can be used as an intake when the airflow is reversed)

As I do not have a PC sitting in a tight spot, I am deploying this baby to my TEC chiller. As hot air rises, I am currently using this air duct as an chimney extending to the ceiling. See pics 3 and 4 for the initial deployment.

Rough cost analysis:-
120x38 Delta fan -$10
120mm 2-meter duct -$6
120 fan filter (guard + retainer) - $1
Zalman fan controller - $3
Extension cables - $1
Fan shroud - $1
$22 bought me a lot of FUN.

As summer is here now (for us in the Northern Hemisphere), everyone stays cool and quiet.
And I hope you enjoy reading this post as much as I enjoy playing around with the chimney.
biggrin.gif
 

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Well, written and excellently documented. Nicely done.

Now, I don't know anything about TEC coolers, but it's usually useless to create an exhaust duct.

An intake duct would take in cool air, increasing cooling performance. But even that is usually not worth it.
 

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How about some temps before and after to see if this is actually a viable solution for some people who might want to mess with this, or something similar, just for the fun of it.

I was thinking of doing some mods in my case and ducting intake from a front fan, through a Push/Pull 212+ and out the back, to see if that would increase temps. I was also planning to try something similar for GPU's, running a slit down the side of the duct or actually making my own little cage that goes close to the mobo. I figured there shouldn't be much air loss through that.

So let us know if this actually helped, I'm curious!
 

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Reminds me of my kitty litter box project. Back in 1981 I had two cats living with me in my apt. To keep the stink away I used an old dog carrier that would hold a kitty litter box. I drilled a hole in the top and put a muffin fan in it - an AC-powered computer fan. I attached a dryer duct, and attached that to a dryer vent (the kind with a flap) mounted on a plank that sat in my window.

Result: no stink in my apt.
 

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I seem to remember someone on spcr who built a literal 5 or 6 foot chimney out of his computer and it reduced temperatures dramatically. Been thinking of doing it myself someday.
 

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Quote:


Originally Posted by systemlayers
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I seem to remember someone on spcr who built a literal 5 or 6 foot chimney out of his computer and it reduced temperatures dramatically. Been thinking of doing it myself someday.

Like this?
It does look extremely tempting except that I haven't got the space.
 

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Quote:


Originally Posted by ehume
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Reminds me of my kitty litter box project. Back in 1981 I had two cats living with me in my apt. To keep the stink away I used an old dog carrier that would hold a kitty litter box. I drilled a hole in the top and put a muffin fan in it - an AC-powered computer fan. I attached a dryer duct, and attached that to a dryer vent (the kind with a flap) mounted on a plank that sat in my window.

Result: no stink in my apt.

Dude thats awesome!
 

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Discussion Starter #9
Update:
My 120mm duct was built with the purpose to convey hot air exhausted from a case (either for the graphics card(s) or for a case rear exhaust. See pic 1) which has little ventilation space at the rear of the case. However, all my PCs are located in well ventilated locations. So, how helpful of this duct for such a situation is still unknown.

However, I have just done a different test:- the duct's own efficiency.

As my TEC chiller (pic 2) is sitting in a wide open location, hot air exhausted from the fans is totally unrestricted in any sense. This forms the ideal condition or the upper boundary for the test.

Brief description of test
A thermal sensor is placed just outside one of the exhaust fan of the TEC chiller. Temp is recorded over a period of 5 minutes. This is the ideal temp (Ti).
Then, the duct is placed over the TEC chiller's fan, making a 90-degree turn bending upward to the ceiling. Total length of the duct is approximately 1 metre. Theoretically speaking, if the duct is at 100% efficiency, then the recorded temp within the duct (Td) should be identical to Ti. In other words, the duct is conveying all the heat from its entrance to its exit end at a rate fast enough causing no thermal backlog. Contrarily, any thermal backlog would raise the Td.

Result
Td is consistently to be found about 3C higher than Ti.

Analysis
-As the 110CFM fan at the exit end of the duct is powerful enough, its being the culprit is ruled out.
-The other possible culprit is the duct. More precisely put, it is the duct diameter. This 120mm duct can match a 120mm fan well. Howerver, this only happens when the duct is fully extended. At its collapsed form, the diameter is only about 90mm. As I bought my duct at 2m length and was extended only 1m long for the test, its diameter is reduced. Coupled with its internal corrugated surface, air flow is impeded. This might be the reason for the thermal backlog. See pic 3.

At a reduced efficiency, using this duct does not help but make worse the TEC chiller.

Tests coming up
1) Retest with the duct at its fully extended length (to achieve max diameter) to see if the efficiency increases to bring Td closer to Ti.
2) Retest with a 160mm extendable duct (which I have already built. See pic 4)
Edit #1: using 160mm duct indeed does bring Td to within 0.5C of Ti. (result as of 29th June 2011)

Now that my main rig is on a tech station, I am doing more 'projects' outside a case than inside a case. I think thermal management outside is just as interesting as inside. Anyone agrees?

(I have changed the title of this thread to 'Thermal management outside a case' and will put all my experience and future projects here.)
 
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