From the following data for the underfeed stoker boiler, find draft required in mm of water column and power required to drive the fan:
Mean temperatures of flue gases
passing through duct – 227 0C
Plenum pressure – 15 cm of water
Atmospheric pressure – 75 cm of Hg
Mean velocity of flue gases in duct – 900 m/min
Length of the duct – 150 m
Mean size of the non-circular duct – 75 cm2k
Number of 900 bends – 4
Number of 450 bends – 4
Loss of draft in every 900 bend – 0.1 cm of water
Draft available from chimney – 1.5 cm of water
Fuel bed resistance for underfeed stoker – 10 cm of water
Fan efficiency – 60%
Motor efficiency – 92.5%
Assuming that 450 bend is equivalent to one-half of 900 bend, resistance offered by non-circular duct is 20% higher than a similar circular duct, friction factor for circular duct is 0.006, find draft required to be produced by fan and the fan power for flue gases. Take R = 294.35