A centrifugal pump having an overall efficiency of 75% requires 6 kW power at 1450 rpm to deliver water against a suction head of 5 m and a delivery head of 12 m. If the pump runs at 1650 rpm and frictional head losses are negligible, the total head developed by the pump in metres will be
Options:
(A) 22.01
(B) 25.05
(C) 29.35
(D) 31.72
Official Answer Key:
A
Step-by-Step Solution & Explanation
Original total head, H₁ = suction head + delivery head = 5+12 = 17 m (power and efficiency data are extra/not needed for this head calculation, since pump affinity laws relate head directly to speed).
By the pump affinity law, H ∝ N²: H₂ = H₁×(N₂/N₁)² = 17×(1650/1450)² = 17×1.2949 = 22.01 m. Answer: (A).
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