免费风机亲和定律计算器
使用亲和定律计算风机在不同转速下的性能。
New Airflow (Q2)
12,500 CFM
New Airflow (Q2) vs Original Airflow (Q1)
公式
## 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.
计算示例
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
常见问题
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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