How Pump Affinity Laws Change Flow, Head, and Power
Wann das zutrifft
Use this guide for rapid what-if checks on variable-speed operation, while being explicit that affinity laws are approximations around similar hydraulic conditions.
Zu verwendendes Tool
Scale flow, head, and power with pump speed using affinity laws.
Pump Affinity Laws Calculator öffnen →Schritte
- 1Start from a known operating point (Q1, H1, P1, N1) on the same pump and impeller.
- 2Set target speed N2 and compute speed ratio r = N2/N1.
- 3Scale flow, head, and power with Q2 = Q1*r, H2 = H1*r^2, P2 = P1*r^3.
- 4Compare scaled point against system curve and motor limits.
- 5Treat the result as screening, then verify with vendor data.
Beispiele
- Estimating energy impact of reducing speed from 50 Hz to 45 Hz.
- Checking whether a small speed increase could recover required head.
Was vermeiden
- Applying affinity laws across very large speed changes without validation.
- Ignoring NPSH and motor current constraints.
- Assuming efficiency stays constant for all operating points.
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FAQ
Do affinity laws replace pump curves?
No. They provide first-order scaling and should be checked against manufacturer performance data.
Can I use this for impeller trim and speed changes together?
Use caution; combined effects need proper vendor-supported methods.