How much electric energy needed to obtain 35mph wind in 4 ft diameter tunnel??

Question

How much electric energy needed to obtain 35mph wind in 4 ft diameter tunnel??

Answer 1

it completly depends on the variable, of which is creating the wind.

if its some homless guy with a chinese fan, no energy is needed, cept of the guys mass.

if its a fan, it depends on the fans motor.

there is never an exact answer. even 2+2 can equal, 2, or 1.

there needs to be the variable. unless you can supply a question with it, it cannot be confidentaly answered.

think of it another way, how hard is it to push that much cubic feet of air?

Answer 2

The horsepower that the motor must deliver to the fan is given by: Brake Horsepower (BHP) = (Flow X Pressure) / (6356 X Fan efficiency)

Flow is in cubic feet per minute (CFM).

Pressure is in inches of water gauge. One inch WG = 0.036 pounds per square inch.

Efficiency is expressed as a decimal, 0.7 rather than 70%.

The area of the tunnel is 4pi or 12.56 square feet. The wind speed is 3080 feet per minute. Flow is 12.56 X 3080 = about 39,000 CFM.

The pressure will be determined by the resistance to flow presented by the structure of the tunnel and whatever is in the tunnel.

The electrical power required to drive the motor is given by:

Watts = BHP X 746 / Motor Efficiency

Motor and fan efficiency are best determined by looking at the manufacturer's published data. If you want to guess, you could use 0.5 for the fan and 0.8 for the motor.

For the air flow resistance pressure, I would guess some where between 1 and 4.

I would guess that the fan brake horsepower might be between 12 and 50 Hp and the motor might require between 11,000 and 47,000 watts.