GATE 2020 CH – Question 53

Fluid Mechanics and Mechanical Operations · Flow through pipes, friction factors, flow meters and pumps · 2 marks · Numerical answer

Water is pumped at 0.02 m³/s between the two open tanks shown. The receiving free surface is 5 m higher. Pipe friction loss is 1 m of water; surface velocities are negligible, water density 1000 kg/m³, g = 9.81 m/s² and pump efficiency 100%. Find pump power in W, to one decimal place.

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Correct answer: 1175.0 to 1180.0

Explanation

The required head is elevation rise plus friction loss, H = 5 + 1 = 6 m. Pressure heads at the open surfaces cancel and their velocity heads are negligible. Hydraulic power is $P=\rho gQH=1000(9.81)(0.02)(6)=1177.2$ W. With 100% efficiency, this is also the required pump input.

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