Question

If the diameter of a centrifugal pump impeller is doubled but the discharge is to remain same, then the head needs to be reduced by

Answer 1

Answer:

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Explanation:

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Answer 2

Answer:

The answer is one-fourth.

Explanation:

i) The head in a centrifugal pump is an analogous physical quantity to pressure.

ii) The discharge in a centrifugal pump is directly proportional to the force it imparts.

iii) As we know,

$Pressure = \frac{Force}{Area}$

iv) Since the area of the pump is directly proportional to the square of the diameter, the area is increased by four times.

New Area = 4 x Old Area

v) The discharge i.e. the force is same.

vi) Hence,

$New Head.New Area = Old Head.OldArea$

$New Head = Old Head . \frac{Old Area}{New Area}$

$New Head= \frac{Old Head}{4}$

vii) Hence, the head needs to be reduced by one-fourth.

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