Stacking fans?

[drewski]

I've got an extra 92mm fan sitting around. What, if any, advantage would it have if I stacked this onto the 92mm exhaust fan I have in back?

Would they just "fight" with each other? (least common CFM or something) or would it actually help the volume throughput out of the case.

 

[WarCon]

If you have a spare fan you should just make yourself a blow hole, that would be much more profitable than stacking them. You might see a little improvement, but one of the biggest problems is heat rises and without a blow hole you can create a nice little temperature layer. Blowholes stop that problem.

 

[etech]

drewski, you have the right idea, unless they are "tuned" to work with each other, the air flow can go down.

Now assuming they were tuned the only way you would see a difference is if they were working against a pressure. Two stacked fans can raise the pressure inside a closed system higher then a single fan. Think of the tubine fans inside of a jet. If the outlet pressures are the same there won't be much if any air flow difference between stacked or single.

But your case should not be that air flow restricive and if it is you would be better off dealing with that problem by opening up holes, installing a lower front fan blowing in or one of the infamous blowholes.

 

[drewski]

Thanks for the replies!

I've got a Fong Kai 320 w/ a 120mm inflo and 92mm exhaust. The mainboard temps I get are ~22-23 degrees. Pretty cool, I think. I was just thinking that the exhaust's mounted close the CPU so maybe a little more juice would help cool the CPU (52 degrees w/ cheapo Taisol & OCZ Gladiator on order).

Not really into cutting the case, especially a top blowhole, as I would have to cut through both the metal structure and the plastic toppiece. That's why I looked for a cool case to begin with. Just looking for something to do with this fan!

 

[Tommahawk]

Fan stacking has to do with air pressure
Fan side by side has to do with increasing air flow when focussed

therefore fan stacking will increase air flow up until the air pressure is equalized. Once this occurs more fans should not increase air flow

Focussed fans in parallel or side by side will increase air flow and air pressure (psi) and that air has to go somewhere and per the paths of least resistance will go into putting extra load on the fans and fan stacking comes into play.

 

[aigomorla]

stacking a fan over a fan will give u very little benifit unless the second fan was set to counter rotate and assist the first fan.

I have been playing with stacked fan setups, and they are not so great.

What you want is a push/pull approach, however this route only works when you need to cheat static.

In an open air fan, your just best with a single fan.