double fans?

I have this interesting idea.
I was thinking of making a sorta double fan setup meaning placing
one fan on top of another for the CPU so in essence creating a much
faster rate of heat transfer thus cooling the CPU a lot more.
Would this be possible or would it make any sense?

If it worked, they would already market commercially available versions. It seems like the bottom one would just cause interference, especially if they were out of sync (and they probably would be)

Okay, noise is doubled, airflow improved by a little.

It does work... to a point. I actually tested this theory once.

You will get just a HINT of more airflow, and a bit more noise over a single fan. They do run a bit faster. I tested this in my old air cooling setup, the fans that were stacked actually ran longer than a single fan before needing maintenance. Possibly due to them helping each other more than increasing airflow. With 6 90mm fans stacked in the lower front intake, 3 stacked above the AGP in the back, and 3 stacked o nthe PSU, and 2 80mm onthe heatsinks, it dropped my temps on a dual 366 Celery(at ~550Mhz) about 6-7 deg F (nothing else changed)

It's the same principle as using a fan on each side of a Heatercore.

I've also found it depends on the internal shape of the fan casing, some are nice & straight, some are angled at the sides.
The straight ones work better stacked, as the angled part didn't create an airtrap(for lack of better word) area.

Finally, I've found it works just a tad better if you have a 1"+ length of tube between the fans for spacing.

So, it does work, barely though. If you have the money for all the fans, and have the power to run them, and also don't mind the noise, if could give you just a few degrees difference.

edit - I also would only stack same model fans.

this 2 fan mod does work ive got 2 90 cm power supply fans screwed together and both of the running at 24 vlt's my idle temps are 31 to 33 depending on the room temp and it goes all the way up to 40 at full load go figure

another slant on this is to gut 1 or 2 fan housings ~~~ seems to help eliminate the dead spot from the fan hub ~~~ for cpu cooling: low or medium speed fans, one seems to work, for high speed fans use two housings ~~~ also could see how this would help for an exhaust fan also, a mini ram effect?

Sorry but somebody allready thought of that idear. Do a search for this fan unit "Thermaltake DU0462-8 Mini Super Orb CPU coolers / Cooling Fans" I think you will be impressed. Also if you search for this you`l prob be able to read some reviews on how well it performs.
Hope this helped a bit.

i read that thier is slight increase air flow but if you could get a fan that spins in the oppisite direction it would help a lot more. the same priciple behind a big boat having two props. they need two to eliminate the tourc of the powerful engine. but it minimizes power loss by having them spin in oppisite directions.