Plant optimization calculator · Updated 17 September 2026
Cooling Tower Fan Affinity Calculator — VFD Speed, Airflow, Pressure & Power
Estimate cooling-tower fan airflow, pressure and power at a new speed using affinity laws, with annual energy difference for VFD screening.
Inputs
Live results
- Speed ratio 0.8
- New airflow 80,000
- New pressure 160
- New ideal power 15.36 kW
- Annual energy difference 73.2 MWh
Formula
Q₂/Q₁=N₂/N₁; ΔP₂/ΔP₁=r²; P₂/P₁=r³.
Worked example
Reducing a 30 kW fan from 100% to 80% speed gives about 15.36 kW ideal affinity power.
Assumptions and limits
- Affinity laws assume similar system/fan behavior and unchanged geometry.
- Minimum tower airflow and thermal performance must be checked separately.
FAQs
What does this Cooling Tower Fan Affinity Calculator calculate?
Estimate cooling-tower fan airflow, pressure and power at a new speed using affinity laws, with annual energy difference for VFD screening.
Can I use this for a final design?
Use it for screening, diagnostics and opportunity sizing. Validate final design against measured plant data, OEM limits and applicable standards.
Why does the calculator show intermediate results?
Intermediate engineering quantities make bad inputs and unrealistic assumptions easier to spot before a decision is made.