A fan is to be selected to ventilate a bathroom whose dimensions are 2 m × 3 m × 3 m. The air velocity is not to
exceed 7 m/s to minimize vibration and noise. The combined
efficiency of the fan–motor unit to be used can be taken to
be 50 percent. If the fan is to replace the entire volume of air
in 15 min, determine (a) the wattage of the fan–motor unit to
be purchased, (b) the diameter of the fan casing, and (c) the
pressure difference across the fan. Take the air density to be
1.25 kg/m3
and disregard the effect of the kinetic energy correction factors.