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

eflyguy · 09-02-09

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?
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hometoast · 09-02-09

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?

Gangleri · 09-02-09

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.

Shadowclock · 09-02-09

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?

eflyguy · 09-02-09

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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Shadowclock · 09-02-09

Quote:

Originally Posted by eflyguy

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)

eflyguy · 09-02-09

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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citat3962 · 09-02-09

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.

Djghost454 · 09-02-09

I have my 360 rad up top with some Nidec high CFM fans sucking into the case, and have all my other fans flipped to exhaust and never had any issues here. Yea, warmer air may blow through the case, but it so far has not affected anything.

Shadowclock · 09-02-09

Quote:

Originally Posted by eflyguy

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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Air flow direction, a challenge..

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