Question

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

Answer 1

The discharge of a centrifugal pump is given by the equation:

$Q = Area$ × Velocity

Q ∝ $D^{2} \sqrt{H}$

Where, D = diameter of the pump impeller

             H = head of the pump impeller

The head of the impeller is related to diameter of the impeller when the  discharge is constant is given as:

                  H ∝ $\frac{1}{D^{4} }$

     That is, $\frac{H_{2} }{H_{1} }$ = $(\frac{D_{1} }{D_{2} }) ^{4}$

Given , $D_{2} = 2D_{1}$

Substituting , we get

           $H_{2} = H_{1} ( \frac{1}{2}) ^{4}$

             $H_{2} =\frac{H_{1} }{16}$

Therefore, the head needs to be reduced by 16 times.

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