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Stupid question about airflow

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Operaghost

[H]ard|Gawd
Joined
Jun 4, 2004
Messages
1,315
I just got a CM HAF 932.

I'm wondering. Which direction do I want to aim the fan on my Xigmatek HDT S1283?

Towards the rear exhaust fan? Towards the top exhaust fan? Towards the front of the case?

I'm assuming I'd want to point it towards an exhaust since I'm pushing hot air at that point no matter what.

Should I point it THROUGH the heatsink fins towards an exhaust or have it "pulling" from the heatsink fins towards an exhaust?

Thanks for any input folks, appreciate it.
 
Top or rear, I think at that point it's just an aesthetic choice and the performance gain/loss is not notable.
 
Fans tend to work better with pushing air than pulling it, so the fan should be pushing through the HS to the exhaust, which it does not matter, so long as it is being exhausted.
 
What about using 2 fans, the stronger one pushing and the weaker one pulling?

Or would that just pretty much be pointless, and I'm just as well of using the single strong fan pushing?
 
Operaghost said:
What about using 2 fans, the stronger one pushing and the weaker one pulling?

Or would that just pretty much be pointless, and I'm just as well of using the single strong fan pushing?
Click to expand...

Fan speeds need to be nearly the same (ie sum of air in approx = sum of air out) otherwise one fan impedes airflow.
You will also note that there is little improvement using one fan in/one fan out on most heatsinks.
Those heatsinks that benefit more have higher resistance to airflow.

You can equate adding another fan in that setup to increasing the torque of a car engine but not increasing the max revs.
The ability to maintain the max airflow of the fan is increased, but the max airflow of the system does not increase any further than the max a single standalone fan can push in open air.
Law of diminishing returns.
 
BlueFireIce said:
Fans tend to work better with pushing air than pulling it, so the fan should be pushing through the HS to the exhaust, which it does not matter, so long as it is being exhausted.
Click to expand...
Not true. Higher airflow fans (>50cfm) work better pushing than pulling, while lower airflow fans (<50cfm) work better pulling than pushing.
 
Great, I'll stick with just the Loon 88cfm 120mm then.

Thanks for the input.
 
Asian PingPong said:
Not true. Higher airflow fans (>50cfm) work better pushing than pulling, while lower airflow fans (<50cfm) work better pulling than pushing.
Click to expand...

In some cases but not on a HS without a shroud, without a shroud the air will just be pulled more from the sides than through the whole HS, path of least resistance and all. You can also get into the whole air temperature and density, but I'm not.
 
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