Air flow direction, a challenge.. - Page 2 - Overclock.net

eflyguy · 09-27-09

Finally got around to doing this, in our living room where ambient is 23C, ceiling fans circulating air although system was in a corner, on a bench. I've got some pics but for now, this is my VM server - a mildly OC'd Q6600 (3.0GHz) in an Antec 300 with an additional 120mm exhaust fan on side vent, as well as the one on the back and the (190?) on top. Two inlet 120's up front. North/South Xiggy 1283 with provided fan blowing up (towards the large fan on top).

Temps recorded:
#1 ambient, sticking out of front panel
#2 between the video card and NB heatsink, about an inch below and in front of CPU fan
#3 immediately after the CPU cooler
#4 in the base of the case where there's little aiflow, between the HD's and PSU

Here's some raw data, about 30min of prime in blend mode before each set of readings:

upright
cpu: 62 62 57 57
tmp: 23 25.9 25.4 32.5

inverted
cpu: 57 57 52 52
tmp: 23 25 25.9 32.5

face up
cpu: 58 58 55 55
tmp: 24 26.4 26.5 34

face-down
cpu: 60 60 56 56
tmp: 23 24 25.7 34.1

normal again
cpu: 60 60 56 56
tmp: 24 26.5 25.9 33.2

Note that all of these temperatures jumped around a little, except for ambient.
..a

Conspiracy · 09-27-09

heat rises. and if u use ur top fan to blow into the case common sense would say ur jsut gunna actually trap heat inside the case.

not sure exactly what im looking at lol

TheJack · 09-27-09

I'm bout to hit you up with a little bit of truth. It doesn't really matter what you do with your fans, but I'll tell you how all my setups look.

I always have at least 1 intake from the side, and some exhaust at the top. Generally the hottest air is near the top of the case, therefore you should exhaust that and not have it blowing back into the case. And, always try to have the same amount of intake and exhaust fans too.

eflyguy · 09-27-09

Quote:

Originally Posted by Conspiracy

heat rises. and if u use ur top fan to blow into the case common sense would say ur jsut gunna actually trap heat inside the case.

.. and these numbers just prove how inaccurate that statement, accepted by many as "absolute truth", actually is..

As far as I can tell, it makes NO DIFFERENCE which direction the fans are blowing as long as you have good flow throughout the case. Good spacing around the case to allow for good inflow and exhaust are equally important.

Heat may rise, but in a case with good airflow, air blowing "down" isn't fighting convection. The air never has time to heat up by any measurable amount - there's simply way too much flow. In every orientation, measured air temps no different - as same with CPU.

This is just like how the temps in a WC loop are pretty much the same within a fraction of a degree, due to the high flow rate. I was not surprised by these findings.

So when you're planning your fan layout, just make sure the case has good airflow. The direction of flow makes no difference, in my opinion, and confirmed by observation.. ..a

Conspiracy · 09-27-09

cool. i might play around with my fans some

eflyguy · 09-28-09

Studying these numbers a bit more, the inverted arrangement actually made the most difference on CPU temps, *but* when returned to upright again later on, the cores didn't get as hot again.

.. so the core temps are really not reliable indicators of cooling performance at different orientations.
..a

Shadowclock · 09-28-09

Quote:

Originally Posted by eflyguy

Studying these numbers a bit more, the inverted arrangement actually made the most difference on CPU temps, *but* when returned to upright again later on, the cores didn't get as hot again.

.. so the core temps are really not reliable indicators of cooling performance at different orientations.
..a

I never really thought that your Core temps would be effected much from case air flow as much as your MB and other component temps would. Would you agree after all the tests? Didn't see your recordings on your other components even though you stated they were recorded.

eflyguy · 09-28-09

That's what the "tmp" readings are, and why I explained (and showed) where I was measuring:

Quote:

Originally Posted by eflyguy

Temps recorded:
#1 ambient, sticking out of front panel
#2 between the video card and NB heatsink, about an inch below and in front of CPU fan
#3 immediately after the CPU cooler
#4 in the base of the case where there's little aiflow, between the HD's and PSU
...
upright
cpu: 62 62 57 57
[b]tmp: 23 25.9 25.4 32.5

inverted
cpu: 57 57 52 52
tmp: 23 25 25.9 32.5

face up
cpu: 58 58 55 55
tmp: 24 26.4 26.5 34

face-down
cpu: 60 60 56 56
tmp: 23 24 25.7 34.1

normal again
cpu: 60 60 56 56
tmp: 24 26.5 25.9 33.2

Shadowclock · 09-28-09

Quote:

Originally Posted by eflyguy

That's what the "tmp" readings are, and why I explained (and showed) where I was measuring:

Ahhh thats what the #1 #2 #3...are...didn't quite get the layout. got it now

Thanks!

EDIT: Good to know at least with your fan setup and your case OR as long as you have good general case air flow that orientation doesn't matter a whole lot.

Nice test +rep

dkev · 09-28-09

Quote:

Originally Posted by eflyguy

.. and these numbers just prove how inaccurate that statement, accepted by many as "absolute truth", actually is..

As far as I can tell, it makes NO DIFFERENCE which direction the fans are blowing as long as you have good flow throughout the case. Good spacing around the case to allow for good inflow and exhaust are equally important.

Heat may rise, but in a case with good airflow, air blowing "down" isn't fighting convection. The air never has time to heat up by any measurable amount - there's simply way too much flow. In every orientation, measured air temps no different - as same with CPU.

This is just like how the temps in a WC loop are pretty much the same within a fraction of a degree, due to the high flow rate. I was not surprised by these findings.

So when you're planning your fan layout, just make sure the case has good airflow. The direction of flow makes no difference, in my opinion, and confirmed by observation.. ..a

No no, the statement is accurate, just not so much in your case. You have a lot of fans moving air and a lot of passive cooling. See you can't really get positive pressure in your case because it will just escape out of the vents and the front bezel. I could turn my fans either way on my scout and it would make little difference for the same reason. Our cases were intentionally designed that way. But for some one that has a "sealed" tower, the preferred way is the right way. The cool intake coming in at the bottom forces the warmer air up and out of the rear upper exhaust. This is physics and not debatable.

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Air flow direction, a challenge..

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