Question

A fan delivers 1.75 cu.m/sec of air at a static pressure of 2.5 cm WG through a circular duct with a diameter of 300 mm and discharges it through a 250 - mm diameter duct. If the fan static efficiency is 76%, determine the brake power input to the fan

Answer 1

the brake power input to the fan :

$BHP = \frac{SP\times CFM}{6356\times \eta_{static}}$

$BHP = \frac{SP\times CFM}{6356\times \eta_{static}}$

Static Pressure (SP) : 2.5  cm WG

CFM – Cubic Feet Per Minute, is the volume of air moved per minute = 3708.03 cfm

Brake Horsepower, is the horsepower absorbed by the fan:

$BHP = \frac{2.5 \times 3708.03}{6356\times 0.76}= 1.92$ W