I have been toying with the idea of how to optimize a case's airflow using standard axial fans for a while now, and so I thought I'd post my thoughts and see what kind of feedback you guys could give me.

Some points I used to exprapolate this drawing:
-Air blowing directly onto the motherboard and video card is superior in cooling to air flowing over them.
-In relation to the first point, the larger the fans blowing onto the mobo, the greater surface area that can be directly cooled.
-Air blowing over a hot device, then over the motherboard (or vise-versa) is inferior to air outside the case.
-A blowhole is needed to remove any excess heat that will rise and isn't cast out by a lower exhaust fan, and from the heat of the bay devices.
-The motherboard should be the primary target for external air.

Some assumptions:
-I am only attempting to determine the optimal course of air flow. The CFM of the fans and sizes of the fans, other than where specified, will be determined by the user.
-The blowhole will discard the small amount of heat produced by the bay devices other than HDDs.
-Any turbulence caused by other sources of air movement inside the case, such as a HSF, and which do not expressly deal with blowing air into or out of the case, are neglected.
-Also, in relation to the first assumption, whether the case will have positive, negative, or no pressure will also be determined by the user.
-Aesthetics were not taken into consideration.
-Other common-sense stuff. (ex. Ambient air will always be cooler than air inside the case)
-A computer with only 1 component of each neccessary for the functionality of the computer was used in this determination.

Now that that's out of the way.... The only intake fans will be located on the side panel and blow directly onto the mobo and vid card. They are 120mm fans. All other fans in the case will be exhaust fans. The HDD will be cooled via a ducting mod. There is a blowhole. That is all. I would like to get your comments and/or suggestions/criticisms. Here is the drawing:

P.S.--This is all theory. I don't have the necessary supplies to test as of yet, but when I do, I'll be sure to test out numerous different configurations, including this one, to see which actually works best.

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Have you done any real testing of this? What were your before and after temps?

Coel is a very good resource and has done numerous airflow/temp testing. I know he has started a few threads and has resonded to many regarding air flow.

Since I'm at work, I cannot take the time to search...I sneak on when I can and for only a few min's.

I disagree with your front bottom as exhaust. It should be intake. Other than that, it is a pretty standard (and well accepted) design.

Ok, I made a few changes after thinking about it a little. I think you're right putwig and I've modified it accordingly. Also, 1 thing I also added is another exhaust need the lower left of the case near the PCI slots. I think this would really help keep them cool and prevent air to stagnate there. I think almost anyone with a mid-tower or larger case could fit 3 40mm fans stacked vertically there, to the left of the PCI slots, or for those with wider cases, a couple of stacked 60mm or even 80mm. What you guys think?

Here is the modified image:

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Upon even further review I have come up with another, possibly even better alternative. In this one all the fans but the blowholes (you'll most likely need a few) are intakes. This way the HDD ducting can be done away with because all the hotter air, after blowing over it, will be sucked straight out the blowholes without fear of heating any other components. Also, this setup will allow for all the components, even the PSU and PCi cards, to be cooled directly by the ambient air. i think someone here already has a similar setup.....was it you AntiM?

Damn I just wish I wouldn't have to wait a few months before testing these hypothesi.

Anyway here it is:

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if you do design #3 then you would need about 3 blowholes on top because then the air will get pumped into the case and just sit there until that one blowholw on top will take care of it. but i think that with 3 high power blow holes on top design number 3 will be the best.

btw i have almost the exact thing to #2 on all my cases so i cant argue with that one it works and thats proven. but you couls always experiment with the third one. good luck

you definatly want the power suppy to exhaust no sense adding that heat if ya dont have to
you may also want to have the upper rear intake be an exhaust because if its right above the graphix card you will be able to suck the heat from the processer and the card out quicker

just one monkeys opinion

A sidebar here ... not truly off topic.

I notice only a few ahve bothered to mount blowers to the *bottom* of the case - why? Is it just the hassle of raising the whole case and making it taller versus how easy it is to add sideholes?

Help a n00b out here ...
-MF

i agree with monkey, no use having the psu blow in because its going to blow hot air onto the CPU,

and if you put a fan in the bottom rear your going to knock out some of your PCI slots, unless you have an extra thick case.

Quote: Originally posted by me_john85 edit, crap pressed quote instead of edit.

There's also that neat little "delete post" option up top too.

In reference to the psu i was thinking if you made a semi-duct to point the flow of air up towards the blowholes instead of down onto the mobo it would still work.

me_john85--I can't imagine any case of size mid-tower or larger with insufficient room alongside the PCI slots to mount at least 3 40mm fans in a vertical fashion. Check your case. I'm sure there's room there.

I've got a Antec SX830 full tower and I could easily fit a couple 60mm fans along side without taking out any PCi slots.

brain fart, i checked for the delete post thing but didnt see it.

and for the fan thing, i dont think that would improve performance much haveing 40mm fans there, but thats why your going to prove me wrong

In image three you have two fans on the same heigth aimed at eachother, that seems like would cause turbulence, especially with side-intakes, it just seems like air would get all clustured up. Use smoke and just watch the air move around, when you get the chance.

Personally, I think three fans on the bottom of the case as intakes would be best, with three blowholes, or two and two etc. etc. With a nice HSF on cpu and chipset would be great. Maybe one side fan just for the cpu.

I actually thought about that too, but then decided the PCI cards and vid card would just block most of the airflow and cause turbulence. Also, the whole motherboard above the VGA card (and on most motherboards that would include the CPU and NB) would get hardly any airflow because it will have to go around the cards. Besides, fans blowing directly onto the mobo have been proven to be superior to linear airflow over the components. Also, that arrangement with only having fans on top and bottom wouldn't cool the HDD whatsoever and leave plenty of dead spots on the sides. Sorry but I don't think that would be a good idea.

After I'm done upgrading components and get a new case I'll buy a boatload of fans and do some tests as to which arrangement works best. Can anyone recommend a way to "see" the airflow but not harm the components or deposit ashes or anything on everything?

There's a special smoke you can use.


I think, then, the best bet would be to have a case where the motherboard mounted to the top of the case, sort of like if you turned your case sideways, I bet that would be awesome......

Except that convection would tend to keep the heat up against the mobo, instead of it rising, and drawing in fresh air below and at the sides...

I've been thinking about small cases recently and I can't help that think a small volume of air might be beneficial, at least in terms of the time to replace all the air in the system. Still, that only works well until you have a fan die, then it all goes to hell fast-like...

EDIT: Could you use dry-ice (CO2) fumes?

DOUBLE EDIT: That'd be a cool way to remove heat from the system... Cool air in... Like A/C... Probably no good long-term, have to watch out for condensation...

people have used Dry-ice to cool computers... then added Liquid Nitrogen and the computer was fully submersed in fluid so condensation wasnt a problem...


edit: heres the linkage to that setup http://www.neoseeker.com/resourcelink.html?rid=57527

Geez, those dudes used Liquid Nitrogen to OC their machine, naturally it froze the thing and trashed the board or OS. Either way, those are some inventive people

actually, most of the parts were in perfect condition until they added the Liquid Nitrogen and get it to like -100 C or whatever

I currently have a mid tower and have 3 80mm fans (two in back and 1 in front) with also a slot cooler for the video card.

Was thinking of adding a fan to the bottom and one at the top?

What do you guys think??

Quote: Originally Posted by putwig I disagree with your front bottom as exhaust. It should be intake. Other than that, it is a pretty standard (and well accepted) design.

-Right on the money!