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Fan Affinity Laws Calculator — result sheet
Estimate how the flow, pressure rise, and shaft power of the same fan change when speed changes.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: r = N₂/N₁; Q₂ = Q₁r; ΔP₂ = ΔP₁r²; P₂ = P₁r³.
The speed-based fan affinity laws provide a first-pass scaling from one measured operating point to another for the same fan. They are useful for comparison, not a replacement for a fan curve or motor and system checks.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Reference speed — rpm; minimum 1.0E-6; maximum 1000000
- Target speed — rpm; minimum 1.0E-6; maximum 1000000
- Reference flow — flow units; minimum 0; maximum 1000000000
- Reference pressure rise — pressure units; minimum 0; maximum 1000000000
- Reference shaft power — power units; minimum 0; maximum 1000000000
Worked example
| Input | Value |
|---|---|
| Reference speed | 1000 |
| Target speed | 800 |
| Reference flow | 10 |
| Reference pressure rise | 500 |
| Reference shaft power | 1000 |
At 80% speed, estimated flow is 8 units, pressure is 320 units, and power is 512 units.
Assumptions and limits
- Fan geometry, gas density, efficiency, and operating similarity remain effectively constant.
- Reference and target quantities use the same units and speed ratio is positive.
- System resistance, stall, noise, motor limits, temperature, and manufacturer performance curves are not modeled.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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