Floor mounted fans?

[3DMike]

I'm thinking of trying a different setup in my next case which I will be building next week. I propose to have 2 120mm fans sucking out the top, and 2 120mm in the floor of the case sucking in. The idea of course is to have as straight an air flow path as possible. Has anyone else tried this? Does it help temp control? But most importantly, how much should I raise the case from the floor so the bottom fans will have enough air to suck?

I'd be real grateful for any suggestions as this next machine will need all the airflow it can get. (Dual athlon, Raid 4 server)

 

[UnseenMenace]

I personally would not use floor mounted fans as thats where the dust is.. Do you really want your system to suck up all the dust from the floor

 

[3DMike]

Of course I'd put filters underneath. But my work room is pretty good in terms of dust. One of my other systems has 250cfm going into it with no filters, it has been running over a year with alomost no trace of visible dirt inside.

As to the space needed under the case, I was thinking that as long as the separation case>floor was greater than the fan diameter I would be ok?

 

[Thelemac]

3DMike (Jul 15, 2001 11:07 a.m.):
Of course I'd put filters underneath. But my work room is pretty good in terms of dust. One of my other systems has 250cfm going into it with no filters, it has been running over a year with alomost no trace of visible dirt inside.

As to the space needed under the case, I was thinking that as long as the separation case>floor was greater than the fan diameter I would be ok?

Actually, I think that would be a tad excessive. I have a couple of programming books under mine right now (two on either side) which gives about two inches of height or so, and that leave plenty of air for the fan to suck up. It is a 120mm fan, too. On my radiator.

 

[3DMike]

The reason I was thinking separation=diameter was from my speaker designing days.....

(paraphrased BIg time!) If a sound source (fan) is opposed by a surface closer than its diameter (floor), a resonance will disrupt sound (air) dispersion and reflection may cause turbulace slowing fan.

Or something.....

I guess I'll just have to try various height until I find the best, then make a permanent stand at that height. Thnx for advice.
M