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I read two different things about the relationship between power (P) of a pump and flow rate (Q). The most common thing that I found was simply that Q is directly proportional to P (power-of-pump). But in Wikipedia: Affinity Laws, it states that Q is proportional to shaft speed (S), and P is proportional to the cube of shaft speed (S^3). This would indicate that Q is proportional to the P^(1/3).

Which is correct?

Arif Zaman
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1 Answers1

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Power consumed by a pump is $P=\Delta p\times Q$, so if the pressure drop $\Delta p$ that the pump must provide is constant then the power $P$ would indeed be proportional to flow rate $Q$. In the Wiki article, impeller diameter is held constant (and not pressure drop) and in that case by dimensional arguments, $P~\alpha~ Q^3$.

Deep
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