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Choosing optimal case airflow


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I'm upgrading my pc and lookinig for advice how to place coolers )



So, the case is Cooler Master 690 II.


I've upgraded from 2500k to 9600k so I decided to change cooling from Coller Master V8 to something new - corsair hydro cooling system.


And this H100i PRO hydro cooler is suggested to be installed as 'intake' cooler, so it will suck cool air from the outside through radiator. This is from manual.


It have two 120mm fans, and 120x240 radiator so I have to choose where is better place to install it in the case: top or bottom?


Here is my thoughts:


1. Top.


If it intake, it will add 75CFM of air, and I have rear 120mm cooler, so the air wil just go out from that cooler.


And I also have front 120mm cooler, so I'll get twice more air intake than exhaust. This is not good, so I have to add additional exhaust. And if I put it at the bottom (the only free place) the air flow will be not really optimal.


The case is divided by VGA card so front intake will just go out via bottom exhaust and top intake will go out with rear exhaust. No motherboard cooling :(



2. Bottom.


As in previous scenario I have to add additional exhaust cooler but in that case I'll get better air flow:


Front intake + bottom intake going through the whole case and out via top + rear exhaust.


All parts (VGA, MB) will be cooled.


But placing H100i at the bottom seems like bad idea because it have radiator which will suck all dust from the bottom.



So what to choose? Or maybe you have other ideas?


I can draw both options if it's hard to understand from text )


Thank you and sorry for my bad english.

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The “for optimal performance install as intake” is one of those disclaimer type statements that should not read as a requirement or even a recommendation. You need to take a meaningful look at each set up. Top exhaust and top intake will probably produce the same results and relative position in the case often has more bearing.


I am assuming the 120mm cooler is on the GPU in some sort of hybrid cooling system. You will always want that as exhaust with its 40-50C exhaust temperature. That also makes the cpu cooler decision really easy - top exhaust. The only meaningful penalty with top exhaust is the influence of GPU heat on the radiator as it would be more affected than in the front. However, since that is not really a factor in a hybrid GPU, you can take the simple option with the easiest hose runs and a very clean and easy airflow. I ran this for quite some time with a Titan X on the 120mm and the case temps were absurdly low and static. In fact, they were better than my current dual 280mm radiator system, at the expense of higher GPU temps.


My general preference is to always dump waste directly out of the case whenever you can. If you can mount the 240mm up top without compromise on the rear 120mm, then that is clearly the way to go.

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It just occured to me you may not have meant a "120mm cooler" to mean a 120mm radiator and GPU cooling system. Rather simply a 120mm fan. If that's true, then analysis is not quite so obvious. I still would recommend front/bottom intake and top/rear exhaust for most people, but if your loads are primarily GPU heavy and the card is dumping a lot of heat in the case, then it can affect coolant temperature as everything in the case warms with GPU waste heat. The advantage of moving it to the front or bottom as intake is not "cooler outside air", but usually moving it away form the GPU. Even in a well ventilated case, there might be a 2-3C difference between the top layer and the bottom. As you mentioned, using in the bottom creates a required monthly dust off and running it to the front is often problematic for multiple reasons on a mid to large conventional tower. Is -2C in CPU temp worth the hassle? That is what you may need to decide, but I would still start with the above top exhaust mount and see how things go before debating less inviting installations.
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