# A REAL, air-tight duct from side of case to CPU fan?



## Studabaker (Mar 28, 2009)

I wanna know about this.  I bet this would be insanely hugely beneficial, but has anyone done it?  Yeah yeah, the cases have ducts and grilles, but what about a truly vacuum proof intake or output of air directly to the side of the case?  What about making air-tight ducts for other things like video cards?

I think I'm on to something here guise.


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## Binge (Mar 28, 2009)

Sure, you could do it, but you mean air tight to the top of the CPU cooler right?  Kind of impossible for a "vacuum seal."


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## Studabaker (Mar 28, 2009)

Binge said:


> Sure, you could do it, but you mean air tight to the top of the CPU cooler right?  Kind of impossible for a "vacuum seal."



why not?  you could put just a little bit of pressure on a rubber o-ring around the edges of the fan and mesh it up with the air duct.


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## coodiggy (Mar 28, 2009)

I've done it a couple way's with good results in regards to CPU temp only: A side panel fan with a duct mounted between the panel fan and CPU heatsink "no fan mounted on the CPU heatsink" and a front mount fan with a velocity stack made out of a plastic flower pot. Velocity stack was taped to the the front of the chassis fan inlet and sealed to the front bezel with hot glue, then a cardboard duct sealed onto the back of the case fan, leading to a PAL HS "also no fan mounted to the heatsink". In both configs the duct was sealed off from the rest of the system, except that it vented from the heatsink, into the case. Sort of neglected the rest of the system in regards to airflow.


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## silkstone (Mar 28, 2009)

^^sounds ghetto.

No reason it shouldn;t work, but good airflow in your case is probably easier and would yield the same results, if not better as the airflow would also cool the other components on the video card.


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## JATownes (Mar 28, 2009)

silkstone said:


> ^^sounds ghetto.
> 
> No reason it shouldn;t work, but good airflow in your case is probably easier and would yield the same results, if not better as the airflow would also cool the other components on the video card.




+1 for good airflow.  If the case moves air well, and efficiently, no need for a duct.


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## Kursah (Mar 28, 2009)

Air ducts are used in pre-builds like Dells where low airflow is a concnern and extracting heat from the heaviest heat output source is required (i.e. cpu cooler), if you have decent case airflow and decent airflow @ the cpu cooler itself there would be no need for a duct and gains from it would be minimal or not even noticable. I made a duct out of cardboard and tape once when i had my e6300 @ 3.5ghz/1.35v and AC F7P, I actually got higher temps with the duct...which went from the intake fan to the exhaust fan. So it really depends on the overall rig, the amount of fans and airflow, and the quality if the cooling imo.


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## coodiggy (Mar 30, 2009)

silkstone said:


> ^^sounds ghetto.
> 
> No reason it shouldn;t work, but good airflow in your case is probably easier and would yield the same results, if not better as the airflow would also cool the other components on the video card.


It was definately ghetto, but the paint job kinda hid the ghetto-ness! That was back when top of the line processors were Thunderbirds n most video cards had passive heatsinks, so yeah, bad idea to neglect the overall case airflow... One of the systems wasn't neglected in regards to case airflow, I added a bigger front intake fan, a bigger heatsink to the chipset and a blowhole with fan on the top case panel. A side panel intake fan was ducted to the CPU heatsink to supply the heatsink with fresh air; Gave pretty good temp results on a 1.2Ghz athlon at 1.3-1.4GHz with relatively tight memory timings. Without the additional fan the CPU was unstable when overclocked. With the fan, it ran solid.  

My current ghetto PC is using the outlet of my radiator fan to cool the board/chipset/ram, with only the PSU fan for exhaust.. I still need to put in some other intake for cooling drives/ passive ramsinks/board/chipset, and possibly another exhaust fan or passive blow hole. 

Overall case airflow is imporatant and shouldn't be overlooked. Keeping the stock case intake/exhaust, or adding to it, to increase case flow, use good wire management, then add another fan to duct fresh inlet air to the CPU heatsink, This SHOULD give you lower CPU temp results compared to just increasing the exhisting case airflow... 

Completely sealed ducting, like with tape, or glue will make it more difficult to change components. Try to make the duct so that it has a foam gasket between the fan/duct, or CPU heatsink, so the duct can be easily removed when you need to get in there to change something.


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## EnglishLion (Apr 16, 2009)

I think a duct from the outside (drawing air in from outside the building) to your intake fan would be beneficial especially in cold countries and during winter.  You would probably also need to reverse the airflow so that the rear of the case was the intake.

But the internal ducting has limited success in my experience - better to 'let it flow'.


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## Studabaker (Apr 16, 2009)

Well, I pulled down the duct that came with my case from where it was (about 3+ inches from the CPU fan) to just over the CPU fan, about a half inch from it, and I think it has made a difference of a couple of degrees.  When I put my hand over the hole for the duct temps immediately jump 1-2 degrees.  I don't understand why you guys don't/didn't/wouldn't think that drawing the coldest air (straight from the room) would help with CPU temps.  IMO it's sort of like a cold air intake.


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## crtecha (Apr 16, 2009)

Pics brotha.  I dig your idea.  I think I may try something similar myself.  Im more soo leaning towards the gfx card option though.


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## silkstone (Apr 16, 2009)

Glad it worked - nowadays most heatsinks are to big to be able to use the side intake vent. Not many people using the standard style hsf anymore.



Studabaker said:


> I don't understand why you guys don't/didn't/wouldn't think that drawing the coldest air (straight from the room) would help with CPU temps.  IMO it's sort of like a cold air intake.



Because with good airflow the air inside your case will be the same temp as the air outside, with the added benifit of being able to cool more components.


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## EnglishLion (Apr 16, 2009)

Studabaker said:


> Well, I pulled down the duct that came with my case from where it was (about 3+ inches from the CPU fan) to just over the CPU fan, about a half inch from it, and I think it has made a difference of a couple of degrees.  When I put my hand over the hole for the duct temps immediately jump 1-2 degrees.  I don't understand why you guys don't/didn't/wouldn't think that drawing the coldest air (straight from the room) would help with CPU temps.  IMO it's sort of like a cold air intake.



If you run a tight duct to your CPU and then cover the intake you starve the cpu of almost all it's air, hence the rise in temps, I'd expect more than a few degrees.  This is not the equivalent of having no duct.  If you use a duct you really need to be using a fan that draws in from the vent and blows down on the cpu, problem then is where does the hot air go?  Usually it spreads in all directions and is not funnelled out of the case.

On the other hand if you encourage a linear flow from front to back and use a cpu cooler that also pushes air in that same motion then all air is quickly vented from the rear of the case.  With a case that has good intake at the front there really shouldn't be any reason for the air to be any hotter when reaching the cpu than if drawn in through the side, unless you have a huge number of HDDs.  The only additional cooling I'd add to my case atm is an additional fan on the rear of the 5.25" drive bays to speed up the air intake to cpu.


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## 1fastbullet (May 3, 2009)

*I'm fixin' to find out*

I just started a project that should shed some light on the subject.
I was given a 4+ year old Dell Dimension about a year ago.  Since then, the (only) fan in the machine has become obnoxiously loud and I decided to do something about it.
If y'all aren't already familiar with a common trick Dell uses in it's computers, it is that the only fan in the machines are ducted with the intention of pulling air in from the front of the case, past the vertically arranged hard drive(s), and then through the fins of the CPU heat sink.  Finally, through this proprietary duct arrangement, the hot air is ducted out the back of the machine.  The fact is, it must work, because they've done it for a  long time, successfully.  (Granted, the anemic qualities of these machines probably make this technique more able to handle the heat generated than a machine of any power).
At any rate, the factory installed fan had to go and I didn't care to find and install an identical fan into the machine, so I opted to install a 120mm into the roof of the machine.  I have completely eliminated the original fan and duct, so I may find that there is a problem with airflow across he passive CPU heat sink and temps try to skyrocket.
My intention is to run the machine without the duct system for a while and see what happens.  Meanwhile, I am in the process of designing and fabricating (or finding and adapting something from a commercial source) a duct system that will blow air onto the CPU, instead of draw air from it as the original duct did.  
At this point, the project is in it's infancy- kindly forgive the lack of "finish" evident in the enclosed photos.  That will (hopefully) come at a later time.  Also, let me mention that I had to do a bit of structural surgery on the machine to facilitate placing the 120mm fan in the roof, forward of the PSU.  It required that the optical drive be moved down one bay and the chassis had to be cut back.


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## Studabaker (May 3, 2009)

1fastbullet said:


> I just started a project that should shed some light on the subject.
> I was given a 4+ year old Dell Dimension about a year ago.  Since then, the (only) fan in the machine has become obnoxiously loud and I decided to do something about it.
> If y'all aren't already familiar with a common trick Dell uses in it's computers, it is that the only fan in the machines are ducted with the intention of pulling air in from the front of the case, past the vertically arranged hard drive(s), and then through the fins of the CPU heat sink.  Finally, through this proprietary duct arrangement, the hot air is ducted out the back of the machine.  The fact is, it must work, because they've done it for a  long time, successfully.  (Granted, the anemic qualities of these machines probably make this technique more able to handle the heat generated than a machine of any power).
> At any rate, the factory installed fan had to go and I didn't care to find and install an identical fan into the machine, so I opted to install a 120mm into the roof of the machine.  I have completely eliminated the original fan and duct, so I may find that there is a problem with airflow across he passive CPU heat sink and temps try to skyrocket.
> ...



Nice.  Good post and welcome to TPU.  Definitely keep us posted!


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## 1fastbullet (May 3, 2009)

*Thank you*

Your acknowledgment is appreciated and I look forward to learning and sharing what I've learned.


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## 1fastbullet (Mar 27, 2010)

Wow, has it really been this long since I posted here?  I intended to return and update before now.

My efforts to create a duct system failed- the little Dimension 3000 case simply doesn't afford enough space to accomplish what I envisioned.  

In addition to the roof-mounted fan, I ended up going with a CPU cooler and fan and a newly installed 120mm fan in the front of the case.  I considered ducting the CPU fan to the side panel but, from past experience, knew it would raise the noise level and decided against it.  My new theory is that filling the case with fresh air from the front, forcing it across the CPU and exhausting it out the top would provide sufficient cooling.  I found a couple Panaflo 92mm fans at Frozen CPU for *99¢ each*, so I bought them in the event I needed additional air flow from the back.  I've not needed them.


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