Radiators perform better when used as an intake. Period.
I very much agree, my testing confirms that also.
This is the result of my testing (originally tested 11/27-31/2013 and retested 3/26/2015).
Everyone's testing WILL vary, but hopefully, this will inspire some others to actually experiment, rather than simply quote the "status quo" as they've read it, rather than actually tested themselves.
My current rendering rig (2xE5-2696 on Gigabyte GA-7PESH3 MB) uses 2 H110 AIO coolers side by side, in a custom polycarbonate frame with a single constant speed 300mm fan above and a single constant speed 300mm fan below (push-pull), spaced 1" from each rad core and designed so that all airflow into the case must go through the rads.
H110s were chosen for both their size AND the fin spacing of the rad.
No air leakage was allowed between the fans and rads, and
proper fan spacing from the rads was used, this is the important part.
Spacing from the rad core matters and I have found that standard "on the rad" mounting is too close.
The highest airflow/velocity is not at the face of the fan, but rather a small distance from it, as with any fan.
This distance varies based on a number of factors (pitch, # of blades, distance from reflecting surface, etc.)
My case is an early server case from the late '90's, same line as this one -
http://www.xlr8yourmac.com/systems/SonofFrankenMac/son_of_frankenmac.html
Mine is 2 - 5.25" bays shorter, being listed as an 11u case on casters, but is also rack mountable.
The case has 2 sections/halves, 1 side for HDDs and the other for the MB.
My custom made rad "box" mounts on top of the case with the 2 H110 rads side-by-side, running across the case.
The top of the case is cut out under the bottom (pull) fan in a 300mm circle that spans both sides/halves equally.
The 300mm fans were selected for their airflow (125cfm) and noise level (22dB-A), not for SP.
SP
actually needed is highly dependent on the rad used and way over emphasized in most cases, mostly because no one
actually tests to see what will
actually work adequately.
The absolute ultimate, perfect, lowest temp cooling setup is only needed by bench queens and not 99.99% of the real world.
Practical has it's place, as does quiet.
Airflow is from the room, above the PC, through the rads, into the case and then out the rear of the case by 2 Cougar Vortex PWM (70.5cfm, 17dB-A) (1 at the rear of each half of the case) and also out the MB side panel by 2 constant speed 220mm fans (110cfm, 21 dB-A).
The 2 - 220mm side fans were not original to the build as there was no problem cooling the CPUs, but were added when a heat build up was noted in the MB VRMs when running a simultaneous load test using IntelBurnTest and GPU-z to test the cooling of the 2 MSI 7970 Lightnings in this build.
As you know, Lightings exhaust the majority of their airflow into the case, rather than out the back and this was causing turbulence, disrupting airflow over the MB VRMs.
The VRM heatsinks are oriented on the MB as to require vertical air flow in a pedestal case.
Adding the side fans solved the turbulence problem, and allowed the the 7970s to not exceed 64c/72c, with secondary card being the higher temp (and indicating the need to check the secondary's OEM TIM install, which has still to be done)
And since airflow is into the case, a 300mm round DEMCifilter screen is used on the rad intake grille to keep the rads clean.
It only requires cleaning once a month and was sourced directly from the manufacturer.
In testing in the 2013 session, my dual E5-2696's (12 cores + 12 Hyperthreaded cores each, total 48 cores) never exceed 52c after 8 hrs (on the highest temp real core), fully loaded (using AIDA 64 (Finalwire)) in a room that started at 26.6c (80F) ambient and finished at 28.9c (84F).
That's 23-26c above ambient, as measured 12" above and to the side of the Rad intake, but not in it's intake air stream so as to keep the digital probe in a still area.
(Room temp itself is controlled by central A/C with the thermostat being located 2 rooms away and set at 26c (79F), so testing (increased room temp) did not start/stop the A/C unit, as the door to the room was closed during testing.)
A second testing session (during the 2013 session), running IntelBurnTest 2.54(LinPack64) (set on maximum stress 100 runs) for 8hrs did raise the temps slightly higher to 56c and room temp to 30c, but that's still only 26c above room temp.
The IntelBurnTest app was able to maitain all 24 cores at 100% and TDP at 118w-119w for each cpu, just under the 120w TDP Intel lists.
(As a side note, if you run the IntelBurnTest app in conjuction with other apps, it should be started first and ended last, BUT ALWAYS check the task manager to make sure it has shut down.
It has a nasty habit of closing the GUI, but leaving linpack64 still running !!)
And please note, these are 8 hour tests, allowing the
entire PC and all it's components to totally heat soak and show any flaws, rather than some short 10-60min. test.
Also note that when full load testing of the dual 7970 Lightnings was done simultaneously with cpu testing (again for 8 hrs.), it had no effect on the cpu max temps, although it did raise the room temp an additional 3c.
All above tests were duplicated (during the 11/2013 testing) with all fans reversed, thereby exhausting all air through the rads.
This was a pain in the a**, as rads as an intake was done first, then all fans reversed to accommodate rads as an exhaust, and then reversing the fans again to return to rads as an intake after finding out that rads as an exhaust raised CPU temps 6-8c (the Lightning's temps stayed the same) in the 8hr tests
8hr tests were rerun in 3/2015
but only using the rads as an intake, which is how the PC has been running since 2013.
All temps for CPUs and the Lightnings were within 1-2c of the original 2013 session, which I consider "margin of error".
Additionally, the original tests (11/2013) were with AS5 as the TIM, and duplicated with Indigo Extreme as the TIM on the cpus.
Indigo Extreme was 3-4c lower in all tests.
(Perfect contact with Indigo Extreme is relatively easy to get with a 2011 socket, as long as the MB is level during the heating/curing process.)
The tests during the 3/2015 session were using only AS5 as the TIM (and naturally only compared to the 2013 tests that used AS5).
Since this was not an extreme cooling case, I decided AS5 works well enough, especially since the expensive Indigo Extreme is destroyed each time the CPU cooler is lifted.
The unit sits about 24" from my right knee and is for all practical purposes silent, only becoming slightly audible when the Lightnings take a heavy load.
Since no attempt at sound deadening was made, some sound absorption material in the case would probably take care of that.
Photos -
http://s172.photobucket.com/user/Micrornd/library/Render Rig?sort=2&page=1
Note that the outside of the case is as-received 10+ years ago.
Please do not upset the flamingo, he's a mean drunk
