Stacking fans?

[Damainman]

What happens when you stack fans on top of each other? Do you get 2x the CFM or something less?

 

[Zepper]

Just on thinking about it for a bit I'd say that you couldn't get more CFM than one of the fans can provide as it is the only one with direct access to the feed air. So you might even get less than the single fan CFM depending on how well the fans are synced. OTOH, the rig might be able to overcome more back pressure thus working better in some applications like CPU cooling on a heatsink.
. I'm sure experimental data is out there somewhere but I'm not aware of it.

..bh.

 

[GalvanizedYankee]

Just because i had heard about this and was testing/playing with a selection of fans at the bench, i gave it a try

Ever hear a twin engine prop plane with the motors out of syncronization. It's like that in minature. I used matched fans and when stacked the noise was much worse=horrid, then when both were running seperatly at 12V.
Air flow will increase by just a tad when stacked but nothing to post or write home about.
The only advantage stacking gives is more mm of H2O will be pulled but again don't write home about it because it's not much.

Counter rotating propellers are for aeroplanes and beanies..

A link of interest...OCers.com...Google stacking fans for more reading pleasure.

Aaahhhh? I would say welcome to the forum but you joined 11 months ago and have a low post count. Kinda quiet aren't we?
Welcome anyway


...Galvanized

 

[grimlykindo]

I did a similar thing in my old DELL PC. I had fans set up as follows:

Back of Case<Fan<Heatsink<Fan

I call it the "sandwich" method

It "forces" air though the heatsink, then directly out of the case

It works very well with minimal turbulance and noise. But it only works on tower heatsinks like on DELLs

 

[Damainman]

"Aaahhhh? I would say welcome to the forum but you joined 11 months ago and have a low post count. Kinda quiet aren't we?
Welcome anyway "

Kind 'uv a lurker, plus I always forget my password,and no, I'm not somebody else under a different screen name!

 

[GalvanizedYankee]

Originally posted by: grimlykindo
I did a similar thing in my old DELL PC. I had fans set up as follows:

Back of Case<Fan<Heatsink<Fan

I call it the "sandwich" method

It "forces" air though the heatsink, then directly out of the case

It works very well with minimal turbulance and noise. But it only works on tower heatsinks like on DELLs

If you go to overclockers.com and look under ducting, there are many set-ups just like your talking about.
Stacking fans would be one right up against the other. Ducted there is resistance and an air cushion between the two. I was thinking of doing a ducted exhaust on my next project.
The two fans would be atleast 8" apart.


...Galvanized

 

[grimlykindo]

Originally posted by: GalvanizedYankee
If you go to overclockers.com and look under ducting, there are many set-ups just like your talking about.
Stacking fans would be one right up against the other. Ducted there is resistance and an air cushion between the two. I was thinking of doing a ducted exhaust on my next project.
The two fans would be atleast 8" apart.


...Galvanized

Yeah ducting has always facinated me, but it seems to only work well with certain cases and fans. It took ALOT of trial and error to finally get mine to work effectively. My final setup was a 80mm fan blowing into the heatsink then exhauseted by a 92mm fan. It seems to work better with a larger fan on the exhaust side.

Let me know if your ducting project is a success, as I am very interested in the idea!

 

[Tweakin]

The biggest gain in this is that you raise the static pressure between the two fans. By doing this, the resistance of the air pressure is lowered and you have increased the efficency of the fans.

I would think there would be no reason to do this unless you are blowing in on one side and sucking out on the other with some object in the middle (cpu cooler) that would benefit from the raised static pressure.

 

[Zap]

Ya know, I've tried stacking fans in open air just for the heck of it (risking my fingers). Funny thing is that some fans will stop spinning.

 

[GalvanizedYankee]

Originally posted by: Zap
Ya know, I've tried stacking fans in open air just for the heck of it (risking my fingers). Funny thing is that some fans will stop spinning.

Hey! Reverse one of them and they won't be fighting eachother. Air flow should all be going in the same direction. You can't have them blowing or sucking at eachother, you know!


...Galvanized