air flow, how much is it needed?

[shankar]

In my other thread i ask for advise about my first mod(you can see a pic of the case there), but now, after reading some guides, and what you say in threads, im in doubt about the air flow, appart from the mod itself.
Everybody mention big fans, a couple of them, lots of air in and out of the case...
i remembre my old pc, an athlon 1.3, that used to be really hot, i bought a copper heatsink with a huge n VERY noisy fan, and even with that the cpu was arround 40ºC, but now i have a athlon 64, with the stock HS, and my mobo (as usual) has fan controller, so usually its RPM dont go higher than 1200 with the CPU at 30~40ºC n lovely silent; so my question is, appart from the look they give to the mod, are those extra fans really needed?

[Omega]

Put it this way, extra fans help cool better, and lower temperatures make things last longer.

However, you want to watch out for pressure (Positive pressure, when the case brings in more than it can push out, and negative pressure, where it pushes out more than it can pull in) as this can make fans ineffecint.

[DaveW]

Actually, most people aim for the case to have a slightly lower pressure on the inside. Pressure is related to temperature and volume, and when the pressure's low and the fans are helping to keep the volume lower, then the air will attempt to absorb heat in order to keep the equilibrium.

The equations are easy, but working out the airflow in your computer is not; hence the reason nobody does it around here.

I'm running a huge amount of fans on my mod, but are they really needed? Probably not to be honest. Things will be cooler, but you'll only need 2 or 3 extra fans max, anything more than that will be a marginal difference.

-Dave

[shankar]

thanks for the info
my case comes with holes tu put a 120 mm fan on the back, but none on the front, so that will have to be modded if i want to keep the preasure as you said.
the only thing i am worried about is the noise, my system run preety quiet now so i don't want to add extra noise if it's not nessesary.
I am not planning to OC right now, so maybe only the HDs may need extra air, I have 2 WD360 raptor, and i found that their temp seems to be a bit higher than 7200 rpm disks.
Originally I was planning not to add any extra fans, but what to you think that will be ok for me?

[DaveW]

To be honest, you can run it fine with a fan to suck air in and a fan to suck air out. Just make sure that the processor is the last place the air visits, or you'll pull hot air through your case for no reason.

Even then, as long as your case has good ventilation, you might not even need to add fans; but i'd recommend erring on the side of caution.

-Dave

[The Modfather]

If noise is an issue, 120mm fans will run quieter and if you use several of them you can scale them down to a lower speed to cut down on the noise even more. I tend to use a lot of fans in my cases but I don't care about the noise. Most of the time my configuration is like this.

1 80mm fan (top, blowhole, out)
2 120mm fans (rear, intake)
2 120mm fans (front, blowing out)
1 80mm fan (side, blowing on the CPU/GPU area)

Using a fan controller to manage the speed of the fans to keep the pressure regulated.

In this instance we're talking about a LianLi PC V2100 full tower case, the proc is a hot running OC'd P4 3.6GHz Prescott core socket 775 at 4.0GHz, 2 Raptor and 2 Caviar HDD, 2 optical drives and dual GeForce 6800 Ultras in SLI. I'm not counting the fans on the proc or the GPU fans in the above list.

My average ambient (case) temperature is around 32c.

I can get the temps lower depending on a few changes.

[DaveW]

Hey Modfather, with that setup aren't you sucking hot air from your processor over your hard drives? If you flipped the front and back fans, you'd be helping your drive a lot, cos i'm pretty certain that the drive won't generate enough heat to make a difference to your CPU temps. Your setup has the CPU getting the coolest air first, but you're keeping the heated air in your case for an uneccessary length of time.

I'm pulling CPU air in from the side and pushing it out the top and back. Air's coming in from the side again over the GPU and getting sucked out the front past my HD. Although i might reverse the second airflow. I'm using 120mm fans for the CPU sucking and 2*80mm for the blowing. Now i think off it i probably will reverse the second airflow, although i might need to put in a 'windbreak' of some kind to stop the airflows contacting and decreasing the airflow efficiency.

Any thoughts?

-Dave

[xmastree]

a 'windbreak' of some kindYeah, eat more beans. ;)

[antheh]

I use a 120mm fan for intake at the front of the case, a 92mm intake fan on the sidepanel and a 120mm fan as exhaust in the back of the case and 2 80mm fans in my power supply, where the 92mm fan blows fresh air onto where the cpu is and the 2 80mm fans in the power supply suck it out and so does the exhaust at the back.

I get good hdd temps, averaging in the lowish 20c's.

[shankar]

thank you guys for your replys. considering what you said, i'll add 2 fans.
i'll place the 120 mm fan that comes with the case, it is at the back, in the line of the CPU, so it'll be blowing out.
i wont put one on the window, im not worried about cpu temp, and i dont like how it looks on that side.
i prefrer to blow the air in where HDs are, i have room just behind them on the other side of the case. besides the HDs are not placed like in a common case, they are parallel to the front, so the air will be passin through them if i place the fans on the side.
what do you think? and considering that there will be a 120mm fan blowing out, which fan/s will be ok for blow in?

[CanaBalistic]

there are sound dampening mats you can get that will cut the noise of louder fans and components.

[The Modfather]

Hey Modfather, with that setup aren't you sucking hot air from your processor over your hard drives? If you flipped the front and back fans, you'd be helping your drive a lot, cos i'm pretty certain that the drive won't generate enough heat to make a difference to your CPU temps. Your setup has the CPU getting the coolest air first, but you're keeping the heated air in your case for an uneccessary length of time.

I'm pulling CPU air in from the side and pushing it out the top and back. Air's coming in from the side again over the GPU and getting sucked out the front past my HD. Although i might reverse the second airflow. I'm using 120mm fans for the CPU sucking and 2*80mm for the blowing. Now i think off it i probably will reverse the second airflow, although i might need to put in a 'windbreak' of some kind to stop the airflows contacting and decreasing the airflow efficiency.

Any thoughts?

-Dave

That'd be true in a normal case but in this case (no pun intended) we're talking about a chambered system, the drives are in a seperate chamber from the mobo so no hot air is transported to them. Here's a diagram of the layout.

http://www.infinity-customs.com/caselayout.jpg

As you can see, no hot air passes over anything that would cause a problem and the airflow is regulated well. The circle on there with the curved arror represents the side 80mm fan, that's pushing air in. There are vents on the front of the case which help keep the pressure regulated as well.

[DaveW]

Nice setup. That's a lot of fans!

-Dave

[The Modfather]

Just 4 fans, that's not much really. I have one rig that has, lemmy count here... ummm... 7 fans, not counting the HSF or GPU fans. Obviously noise isn't a problem for me. :)

I have another case here, no fans, no water cooling, nothing, just heatpipes, doesn't run too hot either.

[DaveW]

How much noise does that make? I don't expect you to have a noise level meter lying around, and i don't even know how decibels works (is it a logarithmic scale?) so i guess between 1 and 10, where 10 is say engine noise from a car and 1 is a laptop CPU cooler?

-Dave

[The Modfather]

In the case I described above? I'd say about a 3 when all fans are running at top speed. The case is acoustic shielded so it's not very loud. Not that I care much really. I can understand why that might be an issue for people who have their machines in their living room, bedroom or other places like that but I've got a home office and to me, the noise is irrelevant, within reason of course. :)