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Affinity Law for Pumps:
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The pump affinity law describes the relationship between pump speed (RPM) and flow rate. It states that the flow rate is directly proportional to the pump speed when all other factors remain constant.
The calculator uses the basic affinity law equation:
Where:
Explanation: The calculator can determine any one missing variable when the other three are known. The relationship shows that changing pump speed directly affects flow rate proportionally.
Details: Understanding this relationship is crucial for pump selection, system design, and energy optimization. It helps predict how flow rate changes with speed adjustments, which is essential for variable speed drive applications.
Tips: Enter any three known values (three of Q1, Q2, N1, N2) and the calculator will compute the fourth. All values must be positive numbers.
Q1: Are affinity laws always accurate?
A: They provide good estimates for centrifugal pumps operating at similar efficiencies, but may be less accurate for positive displacement pumps or when viscosity changes significantly.
Q2: How does speed affect pump power?
A: Power is proportional to the cube of the speed (P ∝ N³), meaning small speed reductions can lead to significant energy savings.
Q3: What are the limitations of this law?
A: It assumes constant pump efficiency and doesn't account for system resistance changes. The relationship becomes less accurate at very low speeds.
Q4: Can I use this for different impeller diameters?
A: No, this calculator is for speed changes only. For diameter changes, a different affinity law applies (Q ∝ D).
Q5: What units should I use?
A: The calculator works with any consistent units (e.g., GPM instead of m³/h), as long as Q1 and Q2 use the same units, and N1 and N2 use the same units.