Question

Problem 1: Water is pumped from a lake to a storage tank 15 m above at a rate of 0.07 m³/s while consuming 15.4 kW of electric power. Disregarding any frictional losses in the pipes and any changes in kinetic energy, determine a) the overall efficiency of the pump-motor unit b) the pressure difference between the inlet and the exit of the pump. Assume the pressure in the storage tank as atmospheric pressure and neglect the velocity of transferring water into the storage tank. Use the efficiency formula as, n = mechanical power transmitted to water (AĖ)/pump power input and take density of water as 1000kg/m³. Hint: For both part a) and b), use the top surface of the lake as position 1 and the free surface of the tank as position 2 (assume the energy level at the exit of the pump is almost same as the entrance of the tank since transmission losses are negligible for a small distance).Ans a) 66.9% b) 147.1 KPa

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