A three stage centrifugal pump discharges water at a rate of 2400 litre per minute at a total head of 36 m. If the pump is directly connected to an electric motor operating at 1440 revolutions per minute, its specific speed will be
Options:
(A) 41.92
(B) 44.67
(C) 51.16
(D) 54.65
Official Answer Key:
B
Step-by-Step Solution & Explanation
For a multi-stage pump, specific speed is computed per stage: head per stage = 36/3 = 12 m. Q = 2400 L/min = 0.04 m³/s. Specific speed (metric form): Ns = N√Q / H^0.75 = 1440 × √0.04 / 12^0.75 = 1440 × 0.20 / 6.443 = 288/6.443 = 44.69 ≈ 44.67, matching option (B).
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