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 Post subject: Airflow idea - bottom mounted case fans, passive top exhaust
PostPosted: Wed Jan 29, 2003 3:50 pm 
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Location: Richland, WA
Ok, so I've been tossing about the idea someone mentioned about putting fan(s) in the bottom of the case, and I've come up with something. How well do ya think this would work?

First, the case would need to be on standoff feet, or casters, to provide airflow space underneath the case. Then cut holes for 2 or 3 80mm fans in the bottom of the case. Have those be the only case fans present, to provide nicely positive pressure.

For exhaust purposes, 2 to 3 holes in the top of the case. Close off any rear exhaust outlet (maybe). Options would be to cut another hole in (and above) the PSU and possibly run it with passive cooling, or simply undervolt the PSU fan.

Advantages I see to this are a definite positive pressure. Single fan location(s) making it easier to filter the air. Having the fans on the bottom would probably be quieter than the front.

Disadvantage would be possible lack of airflow over the hard disks (could still use a front mount fan if needed). Having the direct open holes on the top would be a more direct exit for sound than out the back or through the front panel, and might be noisier.

Would probably still need a fan above your CPU HSF of choice, not THAT much airflow through the case (unless you used 4 Deltas).


I'm liking the idea. Especially the ease of mounting a single filter to cover multiple case fans, and having the hot air exit the top of the case where it should be the hottest (but not having a fan there like most top mount blowholes).



Zyzzyx
- realizing this could've gone in the 'Cases' forum, or the 'Fans' one as well

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 Post subject:
PostPosted: Wed Jan 29, 2003 4:19 pm 
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Location: Vancouver, BC, CANADA
Why not use the PSU with or without the fan, as your exhaust port?

This saves cutting more holes and focuses airflow on a potential hot spot.

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PostPosted: Wed Jan 29, 2003 4:41 pm 
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Joined: Fri Oct 04, 2002 9:52 pm
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tell me how it works out, since im the one that brought it up before and im too much of a chickenshit to try it myself, but if it works im taking full credit :D


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 Post subject:
PostPosted: Wed Jan 29, 2003 5:22 pm 
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Location: St Louis (county) Missouri USA
Well I've had a similar setup running for over a year. I raised the computer with some file cabinet castor wheels. Cut a hole for an 80mm fan mounted inside the case blowing upward. Put a pleated paper filter from a lawnmower over the hole on the outside.

This computer sits on carpet, and this lower fan is very quiet. The setup works great. I eliminated my noisy front case fan after I installed this fan. I like the setup enough to recommend it highly.


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 Post subject:
PostPosted: Wed Jan 29, 2003 10:32 pm 
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Well, I am game to try this. Especially since I have no love for my current case. However, with my schedule, it could happen next weekend, but more likely won't happen for at least a month, if not two+. (my usual "I'll get right to it" schedule).


I was thinking of leaving the PSU exhaust open. Trying to figger if it would do better to have more or less exhaust area than intake area?

I'd think more exhaust area would do better, as it would provide less pressure for the fans to push against.

However, less area (PSU exhaust and one hole on top, or maybe JUST the PSU exhaust) could perhaps do better, because of the higher air velocity passing through the PSU (and thus not needing a PSU fan?).


Hrrmmm....



Zyzzyx
- pondering where his Dremel is hiding

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 Post subject:
PostPosted: Thu Jan 30, 2003 5:21 pm 
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Joined: Sun Jan 05, 2003 12:09 pm
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Location: U.K.
Nice idea!
I agree that it could have gone either here or in the cases forum.
It's very like the plan that I described in the cases section:
http://forums.silentpcreview.com//viewtopic.php?t=2887
The only real differences are that I want the air to pass through a radiator on its way out, and I hadn't decided where the holes should be. I don't think I want holes in the top though: best to be able to put things on top of the machine without killing it.

We're both puzzling a bit over how best to divide the outflow between the PSU and the other exit. I have some vague thoughts on this; once they're a little clearer I shall post them either here or in "my" thread in the cases section (or perhaps even in the Fan Controls section if that seems most relevant).

P.S. Zyzzyx, you're "pondering where your Dremel is hiding". Read about tin snips first!
http://forums.silentpcreview.com//viewtopic.php?t=2307


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 Post subject:
PostPosted: Thu Jan 30, 2003 7:36 pm 
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Location: Richland, WA
My thought ramblings on this today would that I would leave the PSU exhaust hole, and also cut a hole in the top of the PSU and case. Also removing as much of the metal case of the PSU as possible. Would think that with only those two exhaust holes, and three intake fans, it could possibly manage enough airflow velocity (venturi effect) to keep the PSU cool without its own fan.

I've backed off thoughts of watercooling for now, but I see how that could also be incorporated, having the exhaust vents behind a radiator.

I'm not too worried about having the holes up top though, with my computers under my desk, they never get anything set upon them, and there's not enough clearance for the cat to think about that space (unlike atop my monitors).

Oh, and very cool post on tin snips. I have spent plenty of time working with metal. Having a good friend who is a fabricator/welder can do that. Too bad he moved across country, I rather miss having access to his welders, vertical mill, lathes, and other goodies. I feel bad that I almost literally hacked out my fan grills with some basic wire cutters. :P Haven't even filed down the remnants. :(


Zyzzyx
- just had a wierd thought of putting the computers OUTSIDE and running the cables in thru my window
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