increase CFM through a single fan port

T

The_Engineer

Gawd
Joined
Mar 20, 2005
Messages
665
Being the engineer-in-training that I am :eek: I was thinking too much about cooling fans today. I know there are such things on helicopters and boat propellers as 'counter-rotating' propellers. I have seen them in action and they increase the efficency of the 'lift' or 'push' of the prop in its respective medium. I was wondering if there was a way to do a mod where you would take say, 2x 80mm fans, swap the poles electrically on one, flip it over, and have counter-rotating propellers that push the air in the same direction... I am going to have to make some sketches to see if I am just insane or if it is even possible for something like this to work, let alone push more or less air than one fan. Just looking for any other semi-intelligent input on this subject. thanks.
 
Counter rotating props are usually to balance rotating torque forces more than they are to increase efficiency.

And PC fans do not work right if you spin them backwards. Also I think you are thinking of contra rotating props like on some WW2 warplanes.
 
There's a few Delta omg-high-speed fans that do this. For everything else, it's not worth it.
 
3 times the airflow but sounds like a jet engine..... 3 times air flow.... jet engine..... personally i couldnt live with the noise.

Shaden
 
This dual motor 76 millimeter thick fan spits out just as much as TFB1212GHE with up to SIX dB less (2x quieter), producing the most efficient CFM to Decibel ratio of airflow on the market.
Click to expand...
http://www.sidewindercomputers.com/de12gf.html

The fan reffered to in the quote puts out ~220CFM and rings in at 65DB, That puts this fan right near 60DB. This is the range of normal conversation... most certainly not a jet engine. when it is going to be in my basement as a server anyhow i just might be picking one of these puppies up to cool my 12 hard disks....

Normal Conversation
1*10-6 W/m2
60 dB

Front Rows of Rock Concert
1*10-1 W/m2
110 dB

***pain threshold in here somewhere****

Military Jet Takeoff:
1*102 W/m2
140 dB
 
Sound quality is more important than power... Ambient noise, at 60db, is a LOT more distracting and annoying than purposeful, sporadic, conversation... Noise tolerance decreases with consistency over 40dba... a conversation puts out much less sound energy per given unit of time than a constant 60dba white noise source. Trust me.

Not a bad idea if you're going to be more than 10 feet away from it though.
 
Arcygenical said:
Sound quality is more important than power... Ambient noise, at 60db, is a LOT more distracting and annoying than purposeful, sporadic, conversation... Noise tolerance decreases with consistency over 40dba... a conversation puts out much less sound energy per given unit of time than a constant 60dba white noise source. Trust me.
Click to expand...
And I haven't yet seen any review which would confirm that any specified noise level is even close to true.
Apparently manufacturers measure noise from inside building in other side of road.
 
E.T said:
And I haven't yet seen any review which would confirm that any specified noise level is even close to true.
Apparently manufacturers measure noise from inside building in other side of road.
Click to expand...

Amen to that as well...

Delta's pretty damn close if you know the terms they use to measure.
 
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