I once bought a 24" box fan at he HD. It had about 5 narrow blades and it
looked like it would throw a lot of air.
I returned it after 20 minutes. It just made a lot of noise and did nothing
but churn air. Too much turbulence and not enough air movement.
After many years of experimentation I have settled for 3 blades, low speed,
high angle of attack, like shoveling snow with a biiig shovel.
Ceiling fans are also low speed because you want to keep the noise and
vibration down. They, too, benefit from the same principle: Wide blades (3
or 5), low speed, high angle of attack (slope).
Air plane propellers are faced with different dynamics: Small planes
universally have a two bladed propeller. Makes a lot of noise and shoves a
lot of air because there is no churning. But, you don't want your ceiling
fan to rotate at 4000 rpm.
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