All fans to exhaust?

aelfwyne

Member
Dec 10, 2004
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My dad picked me up an Ultra Aluminus Case the other day at Fry's for $69 with a $60 MIR, for a grand total of $9.... I'll be heading into Houston over the thanksgiving holiday and picking it up, to rebuild my system with the new ASRock mobo and my Opteron 170.

It has 120mm fan mounts, as well as a "vga vent" and CPU air duct on the side...

I also have a 3.5" floppy bay exhaust fan that I can use in the case as well.

Since I have 4 hard drives, any air that is brought in through the front of the case ends up being warmed up a lot before it hits the components anyway.

So, my question is - with the side vents as intake (without fans), can all fans in the system be set to exhaust, thus pulling air in through the side, immediately across the CPU and Video card? Would this be viable?
 

Stillhouse

Junior Member
May 17, 2006
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Personally, I'd keep the front as an intake, that way you'd be moving the air off the HDs and keeping them cool while also improving overall airflow.
 

beemercer

Senior member
Feb 10, 2006
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Originally posted by: Stillhouse
Personally, I'd keep the front as an intake, that way you'd be moving the air off the HDs and keeping them cool while also improving overall airflow.

Seconded.
 

SparkyJJO

Lifer
May 16, 2002
13,357
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The HD's don't heat the air up that much. Keep the front fans as intakes and the rears as exhaust.
 

Ayah

Platinum Member
Jan 1, 2006
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You'd have alot of dust building up in the middle then from all the teeny little gaps in your case.
 

LouPoir

Lifer
Mar 17, 2000
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Originally posted by: beemercer
Originally posted by: Stillhouse
Personally, I'd keep the front as an intake, that way you'd be moving the air off the HDs and keeping them cool while also improving overall airflow.

Seconded.

Third - front intake - all others exhaust
 

aelfwyne

Member
Dec 10, 2004
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I guess I'm just going to have to test it... I think front as intake may work the best, but I'm going to try both ways... As far as the hard drives not generating heat... not so - they generate more heat than anything else in my case. Two SATA drives, Seagate 200gb and Maxtor 80gb, plus two IDE drives, both Maxtor 160gb, make for a LOT of heat. I had the Maxtors in an external enclosure, but the enclosure died, so back in the case they went...
 

soybeast

Senior member
Apr 26, 2006
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I read somewhere you should have more intake than outtake to creative positive or negative pressure inside your case. This way less dust builds up inside
 

Canai

Diamond Member
Oct 4, 2006
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Originally posted by: soybeast
I read somewhere you should have more intake than outtake to creative positive or negative pressure inside your case. This way less dust builds up inside

The more air that is going into the case the more dust will go in. Having more exhaust simply makes the air get sucked in through little cracks and holes and the dust builds up there.

You want more exhaust than intake because if you create a negative pressure in the case the incoming air expands, cooling off as it does so. More intake = more air in a smaller space = more vibrating molecules in a set space = increased heat.
 

Injury

Lifer
Jul 19, 2004
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There's lots of myths to intake/exhaust and there are too many cases and configurations to say one way or another.

The best way to do it is trial and error. Change a fan's direction every week and see if the temps go up or down. In most situations you won't see too much change, as the case can never been cooler than the room its in.
 

Fike

Senior member
Oct 2, 2001
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I have noticed that I have lower temps with both of my auxilliary fans blowing into the case, so the only exhaust fan is in the power supply. My case has so many small gaps and holes, that I doubt that I ever could get very much flow from front to back--especially with all the cables, wires, cards and stuff running through the case.
 

Griswold

Senior member
Dec 24, 2004
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Originally posted by: Canai

You want more exhaust than intake because if you create a negative pressure in the case the incoming air expands, cooling off as it does so. More intake = more air in a smaller space = more vibrating molecules in a set space = increased heat.

Sorry to bust your bubble, but the fans we're talking about do not generate enough pressure for that effect to occur - and certainly not in any computer case that is not sealed properly in the first place. So, forget about that.



 

Canai

Diamond Member
Oct 4, 2006
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Originally posted by: Griswold
Originally posted by: Canai

You want more exhaust than intake because if you create a negative pressure in the case the incoming air expands, cooling off as it does so. More intake = more air in a smaller space = more vibrating molecules in a set space = increased heat.

Sorry to bust your bubble, but the fans we're talking about do not generate enough pressure for that effect to occur - and certainly not in any computer case that is not sealed properly in the first place. So, forget about that.

Actually the fans are quite capable of causing a pressure change inside the case. Any air movement (via fan) in or out that does not have and equal opposite (fan) airflow will change the pressure in the case. Why else would air from outside the case flow in (or vice versa)?

I have a small negative pressure in my case which allows me to cool the mobo to ambient+1ºC and cpu to ambient+3ºC. If I turn my exhausts down the temps go up a few degrees.

I know there is a negative pressure because when I turn my exhausts up there is a significant decrease in output from the power supply exhaust.

How do you 'properly' seal a case? I'm not sure what you mean by that :confused:
 

Griswold

Senior member
Dec 24, 2004
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Originally posted by: Canai
Originally posted by: Griswold
Originally posted by: Canai

You want more exhaust than intake because if you create a negative pressure in the case the incoming air expands, cooling off as it does so. More intake = more air in a smaller space = more vibrating molecules in a set space = increased heat.

Sorry to bust your bubble, but the fans we're talking about do not generate enough pressure for that effect to occur - and certainly not in any computer case that is not sealed properly in the first place. So, forget about that.

Actually the fans are quite capable of causing a pressure change inside the case. Any air movement (via fan) in or out that does not have and equal opposite (fan) airflow will change the pressure in the case. Why else would air from outside the case flow in (or vice versa)?

I have a small negative pressure in my case which allows me to cool the mobo to ambient+1ºC and cpu to ambient+3ºC. If I turn my exhausts down the temps go up a few degrees.

I know there is a negative pressure because when I turn my exhausts up there is a significant decrease in output from the power supply exhaust.

How do you 'properly' seal a case? I'm not sure what you mean by that :confused:

What you described is the adiabatic process. Not only does it not work in a computer case (because it is not sealed off), the fans we use here also do not generate enough pressure, or in your example, negative pressure inside the case. What you need is a completely sealed case and radial fans and even then we're talking about maybe half a degree lower temperature at most due to the adiabatic effect.

Nobody questions that these axial fans can produce a low negative pressure inside a computer case (dust bunnies in each corner are evidence) but this is far from being enough for adiabatic cooling, as you described in your first post. Not to mention that air is also not an ideal medium for this unless you take another step and use a compressor.