Noctua NH-D15 pointing bottom->top OR front->rear recomendation

indy17 · Aug 30, 2014

I want to get the NH-D15 for my to be built build (which is this one http://pcpartpicker.com/p/whpCZL) and make a negative pressure case (the case will be wooden, I`ll make it by hand

).

I want to put a big 230-240 mm fan on the side blowing right at the PCIe slots (eg Graphics card), another 140 mm intake from the front bottom, the PSU will be place rear bottom.
As exhaust, i want to use another big fan (eg 230-240 mm - http://www.frozencpu.com/products/12861/fan-836/BitFenix_Spectre_All_White_230mm_Fan_BFF-SCF-23030WW-RP.html?tl=g36c15s1393#blank) on the same line as the NH-D15 fans (so the heat goes all the way outside), and another 140 mm fan which will be placed depending on the NH-D15 facing direction (in order to get the negative CFM).
To be noted that I`ll be using Noctua fans so I might aswell use higher RPMs on the top and lower RPMs in the bottom in order to be able to get the negative CFM.

So, from physics 101, I know that hotter air goes up, so obviously NH-D15 facing up would be better. But then, the Graphics Card would be too close to it, which is why my intention is to put it into the second PCIe slot (not the 1st one).

Do you think this is feasible or the front to rear combination is better? And if so, why?

Thanks
indy

PS: the GPU will come later.

Darkbreeze · Aug 30, 2014

The best configuration is always a front to back airflow path, but may not always be possible depending on the socket and the rest of the configuration.

So I'd go with a front intake 200mm or larger, two top exhausts of 140mm or a single top 200mm, a rear upper exhaust 140 mm and a side intake of whatever size you like. Obviously larger fans equals either better cooling at equal noise levels (As smaller fans) or equal cooling but with lower noise levels.

indy17 · Aug 30, 2014

I think I`m getting the point.
Pointing it to the rear, you can have better cooling as the bottom to top air flow will cool the heat sink from its side (kind of cross cooling - interior is pointing rear, exterior pointing top).
Correct me if I`m wrong concerning this, please!

As for the fans, I`m inclined to think that bigger fans would be better too, as those that I`ve showed till now are <20 dCB.
Would I need another intake facing from front to rear on the same line with the coolers fans, or the bottom front 140 mm + side 230 mm would be enough?
If i put 230 mm top exhaust, 230 mm rear exhaust (same line with the cooler), and 140 + 230 bottom intake (the 2 I specified above!), I get negative pressure and I think i can chill.

Thanks
indy

Darkbreeze · Aug 30, 2014

I don't think you need two front intakes if you're using a 230mm in the front bottom. The side fan blowing down on the VRM's and GPU is a good idea though. The lines are not as important as you might think, although you don't just want everything swirling around with NO directional plan, because the air in the case is exchanged, in optimal arrangements, as much as 1.5x per second.

The most important factors to consider are interference of airflow from interior components like hard drive cages and cabling, (You obviously want these out of the way as much as possible. Mounting hard drives to the bottom of the enclosure out of the way and down where the cooler air naturally occurs is a good way to kill two birds with one stone as long as you leave a small amount of space between the drive and the case so heat can't become trapped.) and personally I'm in favor of an equalized air flow solution, neither positive nor negative pressure, as long as equalization is due to equivalent air exchange rates rather than poorly sealed cases.

Direct airflow onto the board is important too when using a tower cooler rather than a top down or down draft cooler since it won't provide any direct airflow to the motherboard components so a side fan or custom mounted interior fan directed at those components is helpful.

chris_shadez · Aug 31, 2014

Physics 101, yes hot air rises. BUT... The airflow within the case is Intake at front pushes air to rear exhaust which pulls it out the rear of course.
You don't want the airflow to be circulating... in circles or twisting around due to strong exhausts at top too, before being exhausted both top and rear, would be inefficient. Slower exhaust at top would be fine but you want to maintain that front intake to rear exhaust primary flow.

Best position for the NH-D15 would be to go with that primary case air flow of front intake to rear exhaust, so the noctua positioned likewise

Darkbreeze · Sep 1, 2014

Yeah, that's what we said. Thanks for making it redundant. Just kidding.

Pondering · Sep 1, 2014

The cost for positive isn't that bad. I got the cougar hydro bearing 3 pin fans for $6 each after $10 rebate and cougar hydro bearing PWM / 4 pin fans for $5 each after $10 rebate. General flow is always bottom front intake and top exhaust/CPU heatsink with high quality fans then. The quality of the rear exhaust isn't important as long as long as it is a fan that is running. 2 quality fans running intake will still maintain positive airflow with 1 quality exhaust fan, 1 low power fan exhaust along with a 140 mm power supply fan pulling air out / exhausting air in a fan facing up orientation.

The main difficulty with wooden cases is mechanical hard drive mounting. Best of luck.

Darkbreeze · Sep 1, 2014

Pondering :

And trying to find a ground. Heh.

Darkbreeze · Sep 1, 2014

Anybody putting as much time into it as the OP is should probably not use ANY cheap fans. I'd recommend getting ALL decent quality PWM fans for all the intakes and exhausts.

indy17 · Sep 1, 2014

Heh! The "very silent" build that I want will definitely NOT come true if i use random fans.

But I think that an efficient cooling also brings to the silence, plus I can kill two birds with one stone

Cooler components and silent work.

I think due to my English not being native, I haven`t been very clear. So here is a drawing in Paint. The scaling isn`t accurate, obviously

This is to give u an idea.
I also gave "names" to the fans so we don`t mistake them.

To be noted that E1 should be a 230 mm too.
L1 should be 140 mm fan.
L2 - 140 mm (i think)
E2 - 230 mm
The rest is self explanatory.

So, Intake - 2 x 140 + 1 x 230
Exhaust: 2 x 230 mm
BUT as DarkBreez stated, the 230 mm front bottom aka L2 would be enough.
So that would make:
Intake: 2 x 230
Exhaust: 2 x 230?

I didnt quiet get the "finding the ground" thing.
But, to clear things a lil bit: I will prolly dismantle an old case and take the backbone from it and screw it to the wooden case, as getting the exact positioning of the Mobo holes and everything else in the wood would be difficult to say the least.
If you were talking about "ground" as in zero volts, then this i can easily do with what i`ve said earlier and just connect a wire to the ground of the PSU or whatever.

Please, Spock, speak your mind!

chris_shadez · Sep 1, 2014

Darkbreeze :

Got to go for all Noctua fans =) Performance AND Silence

Darkbreeze · Sep 1, 2014

If you live in an area, or your pc is in an area, where it's likely for there to be between an average amount of air particulates and a lot of them, you might want to consider going with positive pressure to discourage dust buildup inside the case which would really only require changing the exhausts to 140mm while leaving the others like they are now OR having 3 230mm intakes and 2 230mm exhaust.

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