Question

Water, with density of 1000 kg/m3 and kinematic viscosity of 1.0 x 10- m2/s, is pumped through a total length of 60 m of pipe from a lower reservoir to a higher reservoir. The inner diameter of the pipe is 30 cm. Both reservoirs are open to the atmosphere, and the water surface of the higher reservoir is 10 m above that of the lower reservoir. The entrance from the lower reservoir to the pipe is sharp-edged, and along the length of pipe there are two 90° threaded elbows (K= 1.5 each) and a fully open globe valve (K= 10). The pump provides a useful pumping power of 40 kW to the water, and the flowrate of water through the pipe is 0.20 m3/s a) Estimate the roughness (in millimeters) of the inner walls of the pipe. [10 marks] In an effort to reduce the required useful pumping power, the globe valve is re a fully open ball valve (K 0.05). Assuming nothing else has changed from your calculation in part (a), what new useful pumping power is required to maintain a flowrate of water of 0.20 m/s? [4 marks] b)

Answer 1

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