Exercise
1) A centrifugal blower takes in 200 m3 /min of air at a pressure and temperature of 101 kN/ m2 and 45° C and delivers it at a pressure of 750 mm of water gauge. Assuming the coefficients of the blower and the drive as 80% and 82% respectively, determine (a) the power required to drive the blower and (b) the pressure and temperature of air at blower exit.
2) A backward-swept centrifugal fan develops a pressure of 80 mm of water gauge. It has an impeller diameter of 0.89 m and runs at 720 rpm. The blade angle at the tip is 39° and the width of the impeller is 0.1m. Assuming a constant radial velocity of 9.15 m/s and density of air as 1.2 kg/ m3 , determine the fan efficiency, discharge and power required.
3) A centrifugal fan discharges 400 m3 /min of air at a static pressure of 40 mm of water gauge when operating at 400 rpm. The power input is 4.5 kW. The diameter of the outlet duct is 60 cm. The pressure losses due to friction from inlet to outlet are negligible. Determine the static and total efficiencies of the fan. Assume pressure and temperatures as 1.013 bar and 200 C respectively. The density of air may be assumed 1.2 kg/m3 .
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