Pump Affinity Laws Calculator
The pump affinity laws calculator helps you quickly estimate how changes in speed or impeller size affect pump performance. It simplifies complex pump calculations into easy, accurate results. Use this tool to optimize flow rate, head, and power in real-world applications.
Affinity Laws Estimator
How to Use Pump Affinity Laws Calculator
Follow these simple steps to use the pump affinity laws calculator effectively:
- Enter the original pump speed (N1) in RPM.
- Input the new pump speed (N2) if speed changes.
- Add the original flow rate (Q1).
- Enter the original head (H1).
- Provide the original power (P1).
- Click calculate to get New flow rate (Q2), New head (H2), and New power (P2).
Tips:
- Use consistent units throughout the calculation.
- Double-check input values to avoid errors.
- Use manufacturer data for accurate base values.
Pump Affinity Laws Calculation Guide
Key Affinity Laws
Pump affinity laws relate speed, flow, head, and power:
- Flow rate: Q ∝ N (Flow is proportional to speed)
- Head: H ∝ N² (Head is proportional to speed squared)
- Power: P ∝ N³ (Power is proportional to speed cubed)
Step-by-Step Calculation Example
Example: A pump operates at Speed (N1) = 1000 RPM, Flow (Q1) = 50 m³/h, Head (H1) = 20 m, and Power (P1) = 5 kW. If the new speed (N2) = 1500 RPM:
Step 1: Calculate flow rate (Q2)
Q2 = Q1 × (N2 / N1)
Q2 = 50 × (1500 / 1000) = 50 × 1.5 = 75 m³/h
Step 2: Calculate head (H2)
H2 = H1 × (N2 / N1)²
H2 = 20 × (1.5)² = 20 × 2.25 = 45 m
Step 3: Calculate power (P2)
P2 = P1 × (N2 / N1)³
P2 = 5 × (1.5)³ = 5 × 3.375 = 16.88 kW
Result: New Flow = 75 m³/h, New Head = 45 m, New Power = 16.88 kW.
Pump Affinity Laws Conversion Chart
| Speed Ratio (N2/N1) | Flow Ratio (Q2/Q1) | Head Ratio (H2/H1) | Power Ratio (P2/P1) |
|---|---|---|---|
| 0.5 | 0.5 | 0.25 | 0.125 |
| 0.75 | 0.75 | 0.56 | 0.42 |
| 1.0 | 1.0 | 1.0 | 1.0 |
| 1.25 | 1.25 | 1.56 | 1.95 |
| 1.5 | 1.5 | 2.25 | 3.38 |
| 2.0 | 2.0 | 4.0 | 8.0 |
Use this chart for quick estimation without full calculation.
FAQs About Pump Affinity Laws Calculator
A pump affinity laws calculator estimates how flow, head, and power change when pump speed or impeller size changes.
Use these laws when adjusting pump speed, selecting a new motor, or optimizing system performance.
They work best for centrifugal pumps under similar operating conditions.
Power depends on the cube of speed. Small speed increases cause large power increases.
Yes. Replace speed ratio with impeller diameter ratio to estimate performance changes.
You can use any consistent units, such as: Flow (m³/h or GPM), Head (meters or feet), and Power (kW or HP).
It provides reliable estimates. For precise design, verify results with manufacturer curves.
They assume constant efficiency. Real systems may vary due to losses or system resistance.