Kostenloser Fan Affinity Laws Rechner
Berechnen Sie new fan airflow, pressure, and power when speed changes unter Verwendung von fan laws. Schätzen Sie VFD energy savings.
New Airflow (Q2)
12,500 CFM
New Airflow (Q2) vs Original Airflow (Q1)
Formel
## Fan Laws (Affinity Laws for Fans) The fan laws are identical in form to the pump affinity laws. They predict how fan performance changes with rotational speed. ### Fan Laws for Speed Change **Q2/Q1 = N2/N1** (airflow scales linearly) **SP2/SP1 = (N2/N1)²** (pressure scales with speed squared) **BHP2/BHP1 = (N2/N1)³** (power scales with speed cubed) A small 10% speed reduction cuts power by 27%, making variable-speed fans highly efficient for part-load operation.
Lösungsbeispiel
A fan at 1200 RPM moves 10,000 CFM at 2.0" w.g. using 5 HP. Speed increased to 1500 RPM.
- 01Speed ratio = 1500 / 1200 = 1.25
- 02Q2 = 10000 × 1.25 = 12,500 CFM
- 03SP2 = 2.0 × 1.25² = 2.0 × 1.5625 = 3.13 in. w.g.
- 04BHP2 = 5 × 1.25³ = 5 × 1.9531 = 9.77 HP
Häufig Gestellte Fragen
Do fan laws apply to all fan types?
Fan laws work best for centrifugal and axial fans operating in the stable range of their curve. They are less accurate near stall or surge conditions, or for fans with inlet guide vanes.
How much energy can a VFD save on a fan?
If a fan operates at 80% airflow, the power is 0.8³ = 0.512 (about 49% savings). At 50% airflow, power is 0.5³ = 0.125 (87.5% savings). The cubic relationship makes VFDs extremely effective.
What about density changes?
For density changes (altitude, temperature): airflow stays the same, but pressure and power both scale linearly with density ratio. This is separate from the speed laws and can be combined with them.
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