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Discussion Starter #1
I believe it doesn't matter which way air flows, as long as it flows cleanly and efficiently.

Like the folks who fret about which way water should flow in a system, with proper flow rates, the actual coolant temp before/after any single component is a fraction of a degree different.

So when you're planning to move air, does it matter if it goes up or down?

I don't think so. I also think you can significantly reduce dust and debris collection by using the top as an intake. There's way too much movement induced by the fans for natural convection to occur or have any impact.

I plan to try this and see what happens, but has anyone come across actual numbers justifying the "accepted" practices?
..a
 

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You're going to change your airflow say, from front to back then back to front and same fore vertical movement?

This actually should be very interesting or extremely boring.. nowhere in between.

Edit: won't you need some sort of symmetrical box for the tests to be useful?
 

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ive been thinking about flipping the air flow around and using positive pressure in my HAF but ive been lazy lately. All the people who have told me that negative pressure is the only way to cool your system havent tried anything else then the typical from bottom to top negative.

hope you do some benchmarks and let us know.
 

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In my estimation front to back and bottom to top is always going to be better...maybe not by a significant amount but it would be more efficient.

Heat travels upward, therefore if your pushing cold air through the top vents then you are essentially fighting a current of hot air...also, any hot air that may sit on top of your case would not get sucked out, it would stay in its little pockets of air between your cool air rushing in. Hard to explain...Not only that but why would you want the hot air being pushed to the front where your face or feet are?
 

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Discussion Starter #5
Winter is coming..


In all seriousness, I am looking prevent dust collection more than anything. My Antec 1200 case has 200mm on top (aprox. 50 square inches) and five 120mm's (about 15 square inches each) between the back (2) and front (3). Of course that's not really as relevant and CFM for each fan, but they are all on low..

Turning the 200 around and using it to blow in, and having the other 5 all suck out, should give me a nice clean air inlet and plenty of air movement. The PSU doesn't move enough air to worry about, but fwiw, it is sucking from inside the case to out..

Again, I believe the amount of airflow induced by the fans is several orders of magnitude higher than any convection due to heating. I don't think it will make a difference in overall temps, but I will test before and after. Not exactly scientific, but I have a 4-channel Sythe fan controller with 4 temp sensors that can be place in different spots in the case (and I'll leave one outside and away, for ambient..)
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Quote:


Originally Posted by eflyguy
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Winter is coming..


In all seriousness, I am looking prevent dust collection more than anything. My Antec 1200 case has 200mm on top (aprox. 50 square inches) and five 120mm's (about 15 square inches each) between the back (2) and front (3). Of course that's not really as relevant and CFM for each fan, but they are all on low..

Turning the 200 around and using it to blow in, and having the other 5 all suck out, should give me a nice clean air inlet and plenty of air movement. The PSU doesn't move enough air to worry about, but fwiw, it is sucking from inside the case to out..

Again, I believe the amount of airflow induced by the fans is several orders of magnitude higher than any convection due to heating. I don't think it will make a difference in overall temps, but I will test before and after. Not exactly scientific, but I have a 4-channel Sythe fan controller with 4 temp sensors that can be place in different spots in the case (and I'll leave one outside and away, for ambient..)
..a

If your worried about dust then make sure all your intake fans have a dust filter on them and keep a positive pressure case so all air coming in is ONLY through the intake fans...all this is covered in my Air Cooling Guide (1st link in sig)
 

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Discussion Starter #7
I've read (and reported to make sticky) your most excellent guide. I just don't agree that airflow direction is a done deal - hence I plan to try it the other way!
Not trying to pick a fight, I just think it can be done differently, and I intend to prove it (but will happily report that I am wrong, if that is the case!)

Dust filters on the fans closest to the floor get full of dust quickly - I know, I've done it. The 1200 actually has removable and easy-to-clean filters on the front fans..
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Interesting Idea.

When I moved my case off my floor I went from finding dust caked on my rad fan filters once every month to not needing to clean them yet in the 2 months since I rearranged my desk. I think the biggest positive change you can make is moving your rig off the floor.
 

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Quote:


Originally Posted by eflyguy
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I've read (and reported to make sticky) your most excellent guide. I just don't agree that airflow direction is a done deal - hence I plan to try it the other way!
Not trying to pick a fight, I just think it can be done differently, and I intend to prove it (but will happily report that I am wrong, if that is the case!)

Dust filters on the fans closest to the floor get full of dust quickly - I know, I've done it. The 1200 actually has removable and easy-to-clean filters on the front fans..
..a

Yea everything I have read on Positive and Negative pressure has been more theory than anything so I would be happy to see any results you may come up with. By the way it is a sticky now so thanks for reporting it


I will say that I do have a positive pressure case since March of this year and I barely have any dust inside at all. Dust around my glass top desk where the computer sits is ridiculous once a week though so I think positive pressure is doing a great job. I even have a mesh vent up top that does not have a fan on it and due to the positive pressure no dust gets in
 

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Discussion Starter #11
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




 

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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
 

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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.
 

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Discussion Starter #14
Quote:


Originally Posted by Conspiracy
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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
 

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cool. i might play around with my fans some
 

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Discussion Starter #16
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
 

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Quote:

Originally Posted by eflyguy View Post
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.
 

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Discussion Starter #18
That's what the "tmp" readings are, and why I explained (and showed) where I was measuring:

Quote:

Originally Posted by eflyguy View Post
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
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

 

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Quote:


Originally Posted by eflyguy
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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
 

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Quote:

Originally Posted by eflyguy View Post
.. 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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