Use IS 80-50-200 centrifugal pump (n=2900r/min) to send 20-degree clean water from the pool to the washing tower at a flow rate of 50m3/h. The working pressure of the tower is 177kpa (gauge pressure), the pipe diameter is 100mm, and the total length of the pipeline (including all local resistances except the outlet resistance of the pipeline). At the specified speed, the performance parameter of the pump is H = 50.0 m. Try to calculate that the percentage of the head lost by the regulating valve to the pump head is close to ().

A 12.74% B 14.74%

C 13.0% D 56.56%

In the figure, the pump foundation is 1m away from the pool water level, and the pipeline outlet is 13m away from the pump foundation.

Choose c, according to Bernoulli equation, the pressure head provided by the pump is equal to overcoming the pressure difference, potential difference and resistance difference. The difference between the calculation head and the pump performance parameter head is the valve resistance. Valve resistance/pump performance parameter pressure head is the answer.

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