A single-stage, single suction centrifugal pump delivers water from a large rese

Question

A single-stage, single suction centrifugal pump delivers water from a large reservoir to an open tank as shown in Figure 4. Steel pipes (f 0.015) of 0.3-m-diameter are used. The suction pipe length is 70m while the pressure pipe length is 200m. The head loss coefficient for the inlet is given as 1.0. The pump is started when the water surface elevation in the tank is 150 m (a) What will be the discharge (in m/s) through the pipe? (plot system curve) (6) What will be the power (in Watts) to be supplied to the pump if the pump efficiency is 65%? (e) Will the pump cavitate (Determined by calculating NPSH)? You may assume atmospheric pressure head as 10.3m, water at T 10C,p 1.23kN/m2, impeller size of 38 cm, and N -1600rpm. (18 poins) Elevation 150 m 90 bend Elevation 118 m Elevation 100.00 m Pump Tank Reservoir Eigure 4 Pumping System (not to scale) 120 N-1600 rpm D- 38cm 100 80 60 40 20 0.05 0.1 0. 02 0.25 30.35 Discharge (m'/s) Eigure S: Pump Head-Discharge Curve

Explanation / Answer

Calculation of total Head

According to bernoulli principle

Total head= Static head+ Head loss due to friction+ Head loss at inlet

Head loss due to friction= 4flv^2/2gD= 4*0.015*270*1/(2*9.81*1000)=0.0008 (assumed velocity of flow =1m/sec)

Head loss at inlet= Kl*V^2/2g= 1*1/2*9.81= 0.05

From the graph

Discharge at 51m head= 0.225 m3/sec

  

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