New case - Best fan configuration?

Caracortada_uk · 23 Apr 2011 at 17:13

Hi all i come seeking your wise advice!

At present my case has 2x120mm front fans (one in the 5.25" bays and one at the bottom), and a 120mm rear exhaust. That set up works perfect.

However my new case has 2x120mm front slots, a 120mm floor slot, 120mm rear slot and 2x120mm roof slots, with the PSU mounted in the floor and a side vent with no fan mounts. So i am a bit confused about the best set up.

I am thinking of just sticking with my current set up but the extra open vents make me wonder if they will interfere with air flow or if i could improve on my current set up. Has anybody a similiar set up and how did you get on?

The case is a Thermaltake V3, CPU cooler will be a Titan Fenrir and the second front fan comes from a case mod.

Thanks.

Kaeo · 23 Apr 2011 at 17:53

Generally speaking, if you have spaces, put fans in them. Open spaces aren't gonna do any good for airflow, at the best.
I usually stick to fronts and sides as intake, and bottoms, back and tops as exhausts. Might wanna mess around with the bottom fan mount though, see if exhaust or intake is better for your temps.

Phenomenologica · 23 Apr 2011 at 18:40

I have two 120's at the front as intakes, one on the side blowing air onto/around my graphics card, an outtake fan at the back, and the PSU also blows air out the back. So basically front to back airflow with one on the side to help cool the GPU.

Caracortada_uk · 23 Apr 2011 at 19:53

The unused grills will be sealed so they will not be an issue, its more how to make use of the spaces i have.

Also the side fan is not an option as there are no mounting slots for it, just a grill.

Caracortada_uk · 23 Apr 2011 at 21:53

Here are some amazing artistic diagrams of the fan placings:

Black = Case
Yellow = Fan slot
Red and Blue are obvious

Current

Flow 1

Flow 2

The current set up works fine for me at the moment giving me temperatures below what others are getting with similiar set ups.

I prefer "Flow 2" as it means air blowing directing only the CPU & RAM and the GPU. But the case is in a restricted space not on an open desk so i am weary of how well it will suck in the air. As such im leaning towards Flow 2, CPU & RAM still get fresh air directly, but the front fan blows air across the HD and onto the GPU.

Empty grills will be blocked up.

Is my logic here correct or can sombody offer a better set up?

Thanks again all.

Si105 · 23 Apr 2011 at 21:57

The general idea with most cases is, the top and back are exhausts and sides, bottom and front are intakes.

EniGmA1981 · 23 Apr 2011 at 22:19

^ exactly what I was going to say!

Anything at the front is a way in, and at the back is a way out... Heat WANTS to rise, so help it out the roof... but it doesn't really want to fall, so pulling the hot air down and out the bottom will possibly have an adverse effect on the airflow...

I've got a floor intake in my HAF but with no dust filter, I've left it clear... the airflow is moving past and away from that grill so there is air being drawn in anyway, I'm just not helping it in

Caracortada_uk · 23 Apr 2011 at 22:34

The top fan is pulling in cold air which likes to fall.

The logic with the top intake is so it blows directly onto the RAM and the CPU. This means the RAM is cooled, the CPU fan has air blown onto it as it sucks it through the heatsink. And hopefully that top case fan will also blow onto the CPU heatsink as an added bonus for extra cooling. It is doing the same job as if it had it in the 5.25" bays but it is right beside them instead.

I find it odd to to have a top fan as an exhaust spitting air out when it is right beside the CPU fan which is also trying to suck the same air flow. If the top fan was moved into the other top fan slot above the CPU cooler exhaust then it would make sense to have it as an exhaust fan so you would have 2 fans pulling out the CPU exhaust.

The CPU cooler could be rotated so it is blowing its exhaust out the top not the rear but this would mean its pulling heat off of the top of the GPU and the chipset.

Phenomenologica · 23 Apr 2011 at 23:30

Caracortada_uk said:
The top fan is pulling in cold air which likes to fall.

Not convinced. Once fans get involved convection in the case is effectively moot. The volume of air computers with multiple fans pull through is huge - My system with three intake fans will draw through a volume of air equivalent to all the air in my room in under 10 minutes. They can completely replace all the air in the case in under a second. Convection doesn't really have time to operate and is a very weak force compared to all the airflow from the fans.

My concern with having the top fan as an intake is that after air leaves the case out the back, it WILL rise by convection as the flow from the fans is gone. Add to that the fact that at the front of the computer air is being drawn in creating an area of lower pressure that will draw some of the air from the back over the top of the computer to the front, especially if the computer is under a desk. That means you're more likely to have air at a higher temperature just above the computer than, say, to the side, so it makes sense to have the top as an outlet.

Just thinking out loud as it were, but from a physics point of view that's the logical conclusion, surely? Realistically though I doubt it makes a lot of odds.

Caracortada_uk · 24 Apr 2011 at 00:03

Hi Phenomenologica, the cold air falls was more in reply to EniGmA1981.

I did not think to take into account air pressure. As the front panels on the 5.25" are mesh im assuming the pressure would balance by pulling air through the panels rather than the top intake air flow. The intake air flow has vertical momentum in a downward direction meaning air pressure would find it hard to balance itself from it compared to external air from through the mesh.

I also understand about having a complete air flow route to not leave dead space. But thought that would be out weighed by the advantage of having a fan so close to the CPU and RAM.

I think i will experiment with the options and report back. I was hoping more to avoid obvious pit falls by asking.

Thanks for the help.

Phenomenologica · 24 Apr 2011 at 00:12

I don't have any top vents on mine so I don't have much experimental evidence. But I did test with no side fan, side input and side extractor, and I got 2 degrees off my graphics card with the air blowing on it. So it's quite possible you are correct about the direct airflow.

The issue is that fluid dynamics is ridiculously complicated, and it would probably take my system running at full throttle a few weeks to accurately model a few minutes airflow in my computer case and the effect that would have on temperatures. So most of the time it's best just to guess, try it out, and see what happens.

Caracortada_uk · 24 Apr 2011 at 00:22

Fluid dynamics still makes my eyes cross at the thought of it. Studied many moons ago but the pain is still fresh

mayebaza · 24 Apr 2011 at 10:20

An overall draft, blowing air in the case upwards over the components that generate heat, from the front to the rear, always produces the best results in cooling and quietness. Inside your case needs to be like catching a chill from sitting in a drafty room because someone left a window slightly open.

Below is picture of my old set up which very similar to your case. I now have the same set up but with better components. Even in this warm weather with a max overclock on my CPU and two graphic cards in crossfire, I can only reach 51 degrees at full load.

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Gigabyte GA-MA790FX-UD5P, 955 BE(C2)@ 3.92GHz 1.52V,Geil Value 4GB DDR3-1600,
ATI 5850 1GB(Crossfire), CM90 II Advanced, 1TB Western Digital Caviar Black, 4 HDDs,
XFX 850W BE, Asus Xonar Essence STX, BlackGold HD DVB-T2, Dual Digital DVB-C.