If you read Corsair's AIO instruction, they explicitly state state to install the fans to blow into the case. We all get that thing from 8th grade earth science stuck in our head ... "Hot Air Rises".... well not when there's a bunch of fans blowing it the other way. When ya get to thermodynamics, "it's clear"... 22C room air cools your components better than 26C air does, the math is inviolate. Your GFXcard and other components are all mini heaters ... do we care if anything else in that case gets a few C warmer ? Not many bother to even measure inside case temps ? When we think about cooling the focus should be on the components that have their performance impacted by higher temps. Another way tolook at it for every CF of air being pushed in , 1 cfm is also being pushed out.
What is rarely considered is heat recycling where the back of the case is near a wall and air exhaused by 300 watt GPUs and the PSU is sucked back in because of negative pressure.
Back in the day when water cooling was a hobbyist realm ... earth science never came into the discussion, just the math. Whether using air or water cooling, it's all about Delta T (difference between air and components / coolant. This was my test bed w/ one 140mm fan at rear out, three 140mm in front in. 60 x 520 rad on top / 80 x 280 rad on bottom.
Top GFX ==>
Dual Pump ==> 280 Rad ==> ==> CPU ==> MoBo Chipset ==> 520 Rad =>Pump
Bottom GFX ==>
10 fans in push - pull intake
vs
10 fans in push - pull exhaust
5 Temperature sensors
520 x 80 rad in
520 x 80 rad out
280 x 80 rad in
280 x 80 rad out
Interior case temp.
Six Eyes Temperature Display
The system was designed for a Delta T of 10C at 880 watts of load measured w/ a power meter. In testing,the push-pull intake resulted in water temps of about 8.4 C above ambient under Furmark , well below the 10 C target .. water temps were about 2C higher on the rad outlets than the rad inlets. Fan speeds were controlled by CPU temps never topped 850 rpm under Furmark and 550 rpm during gaming. I had them turn off if the fan curve reached 400 rpm. In the test with the rad fans exhausting, water temps from the sensors were 1.5 -1.8 higher. GPU an CPU temps were higher but not at a level of concern .... in and of itself other than that all the rad fans started to become audible. Not overly bothersome but just at peak times. And with two GPUs (back in the day when SLI was worthwhile, the CPU was a fraction of the the GPU heat load.
As for the dust, well case designs usually have a fine mesh on top which does a pretty good job as long as you clean it now and then. In most cases, installing a AIO w/3 fans most times this means more fans blowing out then in which = negative pressure. This means that air will be sucked in thru those wide hexogonal openings in the back of the case that you can almost fit a pencil thru. Unless you are a lot better at housekeeping than my youngest son, (you will have spider webs and dust clumps all along the back of the case).
If the smoke is drawn into the case,you are not only sucking in the dust , ..... back against the wall like in most desktop setting," you are sucking in the exhaust from your PSU and GFX card ... which is likely at least 2 times more wattage than your CPU. Every ounce of air blown in has to get out or the case will explode. But on most desks, if you have that 3 fan AIO blowing out, air coming in thru that back panel is usually unavoidable bringing freshly exhaused GPU/PSUheat and dust in.
However, let's look at THIS case image again and remember the conservation of mass law, I see 7 fans blowing in and 1 blowing out. But with 4 in and 4 out do we not have to worry about the appropriatness of a "Hoover" sticker on the case ? That's harder to figure in our heads ... what is the CFM / pressur capability of each fan, how much resistance is each fan experiencing from the dust filters ? Our brains hurting yet ? I enjoy the noggin excercise and will always start w/ a best guess just for the fun of seeing how it turns out. I keep a can of "smoke detector tester" in my toolbox . Alternatives you can use this include a stick of insense held at the back of the case in it's "in use" at your desk position.
During my sons high scool & college years, it was "nerd central" here ... at least once a month one of my sons or one of their friends were here doing a build. Not many went full custom water cooling, most were happy with AIOs both for the lower cost and after the LED thing started that was the "main thing". We always did the smoke tests, if smoke went into the case, that negated the need to go any further. We used the laser gun when we could but if ya had to take the side panel off, actual in use conditions could not be produced.
It's not as if it's 10C difference between the two options,that doesn't mean it doesn't help getting a bit more performance. Science doesn't support the "hot air rises" model. Avoiding negative pressure is the 1st goal. Having the lowest coolant temp is next. Bothnca be measures easily enough but the negative pressure thing is easaierand cheaper.
