FAN EQUATIONS

Output Power


BHP = Q x SP / (6356 x Fan Ef f.)


Where

• BHP = Break Horsepower

• Pt = Total pressure, in-WG

• Q = Air flow rate in CFM

• SP = Static pressure in-WG

• FAN EFF = Fan efficiency usually in 65–85% range


Fan Motor Horsepower

Motor HP = BHP / MotorEFF

Where

• BHP = Break Horsepower

• MotorEFF = Motor drive efficienc y usually 80-95%



Tip Speed

Ts = 3.14 x D x N

Where

• Ts = Fan tip speed, FPM

• D = Fan diameter, ft

• N = Fan speed, RPM


V-belt Length Formula

Once a sheave combination is selected we can calculate approximate belt length. Calculate the approximate V-belt length using the following formula:


L = 2C + 1.57 * (D+d) + (D-d)2/ 4C

Where

• L = Pitch Length of Belt

• C = Center Distance of Sheaves

• D = Pitch Diameter of Large Sheave

• d = Pitch Diameter of Small Sheave