Effect on blocking airflow?

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peterson
Posts: 256
Joined: Sat Jan 15, 2005 2:09 am
Location: Gothenburg, Sweden

Effect on blocking airflow?

Post by peterson » Wed Feb 16, 2005 2:01 am

This question came up in my mind when i was about to install my new PSU in my new case.
Well, it came up a bit earlier but now i decided to dig deeper into it.

My PSU has a 120mm fan at the bottom, and the case has a 'frame' for holding the PSU.
The 'frame' seems to be made for a 92mm bottom fan or similar, so my fan gets a bit obstructed.
Not much, but it caught my attention.

I've read about some people that has cut out their fan grill at the back of the case to get better air flow or lower noise.
But i tested with having a fan blowing and putting it closer and closer to the grill, but i didn't hear any difference at all.
So decided not to cut my case.
But now i became a bit more worried that i shouldn't get max air flow into my PSU.

So, what happens if airflow gets a bit obstructed?
Is there a difference if it's on suck or blow side?

I just imagine that if it gets obstructed a bit on the suck side, air finds another way through at a higher speed.
Up to a certain level of obstruction of course.
And if so, how much more noise does the higher airflow make?

If it's obstructed on the blow side, perhaps it's the same way, it finds another way through at a higher speed.

Or is the airflow reduced with the amount of obstruction?

It's a bit difficult to test for me but perhaps someone in this community has the knowledge already. :)


If i had some bad old 120mm fans, i'd make shrouds of them and put one on my XP-120 CPU cooler for test purpose.
If it's important in watercooling radiators, it should be the same on heatsinks, no?

Thanks!

ferdb
Posts: 124
Joined: Fri Sep 10, 2004 1:13 pm
Location: austin, TX

Post by ferdb » Wed Feb 16, 2005 6:14 am

If your PSU has a thermally controlled fan (speeds up when the PSU gets hotter) then there will probably be little effect other than your fan MAY run a little faster. The original reason that 120mm bottom fans were put in PSU was to help cool the processors back when they were starting to get out of hand thermally, it wasn't really to cool the PSU. That job is mostly done by the rear 80mm fan in the PSU. As PSU designs have evolved though that may not be entirely true anymore. However I doubt that restricting the bottom intake to 92mm is going to have any noticeable effect on your PSU.

Tibors
Patron of SPCR
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Joined: Sun Jul 04, 2004 6:07 am
Location: Houten, The Netherlands, Europe

Post by Tibors » Wed Feb 16, 2005 8:09 am

ferdb,
It might be me, but your post makes absolutely no sense to me.
ferdb wrote:The original reason that 120mm bottom fans were put in PSU was to help cool the processors back when they were starting to get out of hand thermally, it wasn't really to cool the PSU. That job is mostly done by the rear 80mm fan in the PSU.
As I read it you are talking about a PSU that has both a 120mm bottom fan and a 80mm rear fan. I have never, ever seen such a PSU. :?

peterson
Posts: 256
Joined: Sat Jan 15, 2005 2:09 am
Location: Gothenburg, Sweden

Post by peterson » Wed Feb 16, 2005 8:18 am

Well, i got a bit confused too, so thanks Tibors. :)
But that was just a piece of my post/question.

A picture always clears the mist. :)
This is what it looks like.(not my case, just a review of it)
Image

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