If I were to construct a fan 5ft in diameter and I wanted that fan to spin at 40 mph how big of an electrical engine would I need, or rather how many rpms' would it take to acheive that speed?
2007-11-17 11:18:59 · 4 answers · asked by Andrew 3 in Science & Mathematics ➔ Engineering
GATORBAIT, he is talking about RPM dude!
He wants to know what motor hp will speed the fan so the blade tips move at 40 mph.
Why does he wants to do it that way, I have no clue.
#1 The power required will depend on the weigh of the blades and the pitch.
#2 It will depend what type of mechanism will connect the motor and the fan. Will it be pulleys and belts? Gears?
My guess is that any variable speed 10 hp electric motor, most likely 220V will do the job depending on the installation and gear system.
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2007-11-17 12:35:28 · answer #1 · answered by autoglide 3 · 0⤊ 1⤋
At the blade tip, the speed is Pi*D*RPM
For the tip to go 40MPH:
40 miles/hr = Pi * 5 ft * rev/min
rev/min = 40 miles/hr * 5280 ft/1 mile * 1 hr/60 min * 1/5*Pi
RPM = 224 RPM
The motor size would depend on the CFM of air being moved, the RPM of the motor, and the pulley or gear reducer ratio.
2007-11-17 12:37:50 · answer #2 · answered by mechnginear 5 · 0⤊ 0⤋
It would depend on how much air, in cubic feet per minute, that the fan could move at the speed you want, and what amount of static pressure it could develop.
Fan manufacturers design their fans and then test them to determine the volume of air they can move, and the static pressure they can develop using various blade arrangements and blade designs.
If you want to move standard air at 40 miles per hour thru a 5 foot diameter duct, the air would be traveling at 3520 feet per minute x 19.63 square feet = 69,098 cubic feet per minute of air that the fan would have to move.
Then, the total air horsepower required = Ht*CFM/6350
where Ht = total pressure of the air in inches of water.
Assuming a discharge perssure of 3" of water gage, the horsepower required would be :
3*69,098/6,350 = 32.65 Horsepower
If your fan blade only developed a pressure of 1" of water gage, it would only require 10.88 Horspower, but it wouldn't be able to push the air thru as long a duct as the 3" water gage rated blade.
2007-11-17 12:19:00 · answer #3 · answered by gatorbait 7 · 0⤊ 0⤋
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2007-11-17 11:20:58 · answer #4 · answered by dremclovin 1 · 0⤊ 0⤋