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View Full Version : Questions for the CASE COOLING EXPERT!


sillyeagle
11-01-06, 03:35 AM
If one were to put two fans in a case, would it not make the most sense to make both of these exhaust fans?

If a given exhaust fan is moving 200 units per minute, am I correct in assuming there is an implied 200 units of intake?

That being said, two fans would mean there is 400 units moving through the case.

Now since with one exhaust fan there is already 200 out, and 200 in, it seems to me placing the second fan as an intake to funnel the 200 units through a given hole will only marginally increase the total case flow, as it would take away any resistence the exhaust fan encounters in pulling air out of the case, as it is now being pushed out by the other.

So two exhaust would mean 400 units of flow, but I cannot see adding an intake fan along with an exhaust fan will increase the efficiency by 100%, effectivly matching the effectveness of two exhaust fans.

So the question is, why not go with two exhaust, rather than one intake and one exhaust?

The ONLY benefit I can see, is that cold air may be blown directly into the graphics card area as well as on the CPU heatsink. But I wonder how the effectivness of this compares to a higher overall case flow.

If my logic is flawed here please let me know.

CaptNKILL
11-01-06, 08:07 AM
I've often wondered this myself.

Heinz68
11-01-06, 10:05 AM
I have two identical 120mm fans, one intake and one exhaust.
My Enermax PSU also has two fans, creating much more exhaust than intake.
I noticed dust getting in the case through every little opening like around Floppy and DVD drive and even the front USB ports.
Therefore I decided to mod the case and add one more intake fan on the side window, both intake fans will have dust filters.

jAkUp
11-01-06, 11:35 AM
If one were to put two fans in a case, would it not make the most sense to make both of these exhaust fans?

If a given exhaust fan is moving 200 units per minute, am I correct in assuming there is an implied 200 units of intake?

That being said, two fans would mean there is 400 units moving through the case.

Now since with one exhaust fan there is already 200 out, and 200 in, it seems to me placing the second fan as an intake to funnel the 200 units through a given hole will only marginally increase the total case flow, as it would take away any resistence the exhaust fan encounters in pulling air out of the case, as it is now being pushed out by the other.

So two exhaust would mean 400 units of flow, but I cannot see adding an intake fan along with an exhaust fan will increase the efficiency by 100%, effectivly matching the effectveness of two exhaust fans.

So the question is, why not go with two exhaust, rather than one intake and one exhaust?

The ONLY benefit I can see, is that cold air may be blown directly into the graphics card area as well as on the CPU heatsink. But I wonder how the effectivness of this compares to a higher overall case flow.

If my logic is flawed here please let me know.

Reason is you want to direct air. Unless you like cool air coming in through the holes around your lan ports instead of at the bottom/front of the case cooling your cards and CPU :p

Q
11-01-06, 11:56 AM
A lot of his to due with air pressure. It's very unlikely that two exaust fans would be able to draw in enough air to compensate from the air they're trying to push out. You create negative pressure in the case and have dust being sucked in through your PCI slots and Optical Drives.

Hot air rises. You have cool air intakes on the bottom front of a case and an exaust in the back. This creates a flow of air from the bottom, which is cold, and sucks it over the CPU. This way the CPU constantly has non-heated air. It is also why it is vital to have as little clutter as possible in the case.

Your assumptions are based on optimal operating conditions. The two fans would kinda of be canceling each other out to some degree because of the pressure difference.

CaptNKILL
11-01-06, 12:06 PM
A lot of his to due with air pressure. It's very unlikely that two exaust fans would be able to draw in enough air to compensate from the air they're trying to push out. You create negative pressure in the case and have dust being sucked in through your PCI slots and Optical Drives.

Hot air rises. You have cool air intakes on the bottom front of a case and an exaust in the back. This creates a flow of air from the bottom, which is cold, and sucks it over the CPU. This way the CPU constantly has non-heated air. It is also why it is vital to have as little clutter as possible in the case.

Your assumptions are based on optimal operating conditions. The two fans would kinda of be canceling each other out to some degree because of the pressure difference.
Makes perfect sense. :)

nekrosoft13
11-01-06, 12:12 PM
i have quite a few fans

all of following are 120mm
1 intake in front
2 intake on side
1 exhaust in back
1 on cpu heatsink
1 on top

and one 80mm (soon to be replaced by 120mm) blowing on GX2 from the end

Bman212121
11-01-06, 12:26 PM
I know the easy way to solve the problem.

1. Removed the side panel on the case.
2. get an ordinary house fan.
3. attach it to the side of the case.

:D

walterman
11-01-06, 12:44 PM
In all my experiments, i found that there's a huge difference if you put 1 fan in the side of the case blowing air directy to the cpu cooler.

ViN86
11-01-06, 01:55 PM
this will sound noobish, but ive always found its best to try different in/out combos then play a game and monitor temps.

worked for me in the past lol

right now i have an intake over my cpu and an output at the top of my case by my vid card. i have a baffle directing air directly onto my cpu HSF. i have an intake at the front too.

Dazz
11-03-06, 12:01 PM
Well i have an Cooler Master RC830 case that have 3x 140mm fans on the side
1x 120mm front, 1x 120mm top blowing out, 1x 120mm back 1x 120mm on PSU 1 x120mm on Thermalright HSF forcing the air upto the top of the case.

Over all there is 225CFM's in and 135CFM's out excluding VGA and CPU fans of course. Max noise is 30dBA which is the 1700rpm fan on the CPU. I have tried reversing the side fans my idel temps had gone down but my load temps increased. Over all my CPU temp is 39C idle and 58C underload, this is 100% load after 4 hours on both cores and 1.65v 2.2GHz X2 @ 2.66GHz. 2.75Ghz is stable for everything but battlefield2 :rolleyes:

mullet
11-03-06, 04:48 PM
This is simple, you want to make sure that you match the CFM's coming in that is going out the main objective is to change the air in the case as fast as possible. You don't want to have - pressure or + pressure you want it balanced. In the end if you can take your case door off and your temps go up on your cpu & GPU then you have the right balance. I plug every hole in my case to make sure that the air coming into the case is through the fans only. I hate dust in a case, the silverstone TJ-03 has a air filter in the front which I love and it keeps my case almost dust free. To be honest I have been thinking of designing and building my own case, even though I love my silverstone and some other case's it never has the fan size and configuration I like. Maybe I will get off my ass and come up with something.

my 2 cents.

Levell0rd
11-06-06, 02:05 PM
i have quite a few fans

all of following are 120mm
1 intake in front
2 intake on side
1 exhaust in back
1 on cpu heatsink
1 on top

and one 80mm (soon to be replaced by 120mm) blowing on GX2 from the end

That's not a lot... My last case:

2 front 80mm intake, 2 rear 92mm exhaust, top 120mm exhaust, 2 50mm bay fans for exhaust, 120mm side intake, two 80mm in my PSU, one 92mm on my CPU, a 40mm on the northbridge, and one PCI slot fan.

Lucky 13.

My current case:

Three top 120mm exhaust, front, side, rear 120mm intake, chipset 40mm, 92mm CPU fan, 120mm PSU intake, 80mm PSU exhaust, 70mm NV5 Rev3.

Down to 11.

Difference between the two cases? One was a jet and the latter in inaudible. Loudest fan is 21dB.