What are the pump affinity laws and how are they applied?

Affinity laws relate pump performance parameters to speed changes: Q2/Q1 = N2/N1 (flow proportional to speed), H2/H1 = (N2/N1)^2 (head proportional to speed squared), P2/P1 = (N2/N1)^3 (power proportional to speed cubed). Applications: predict performance at different speeds, evaluate VFD (variable frequency drive) energy savings, and estimate impeller diameter changes. Limitations: only valid for geometrically similar conditions, inaccurate at low speeds or significant efficiency changes.