What is specific speed?

Dimensionless parameter characterizing impeller geometry. Same Ns=similar machines.

SI: RPM, m³/s, meters. Different units give different Ns values.

Can I use Ns for fans?

Yes. Replace head with ΔP/ρ. Same impeller type guidance.

Peak efficiency: Ns=40-80 for centrifugal pumps.

Free Engineering Tool — #161

Ns=n√Q/H^(3/4). Determine recommended impeller type.

Ns=n√Q/H^(3/4)Impeller Type

Specific Speed (Ns)

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Recommended Impeller

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ω (rad/s)

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Flow (m³/h)

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