If the wheel velocity is constant - the affinity laws for change in impeller diameter can be simplified to
q 1 / q 2 = (d 1 / d 2 ) 3 (1b)
dp 1 / dp 2 = (d 1 / d 2 ) 2 (2b)
P 1 / P 2 = (d 1 / d 2 ) 5 (3b)
Replace the default values with the actual values. The calculator is generic and can be used with all common units as long as the use is consistent.
Use of the fan laws can sometimes be simplified by using Equivalent Static Pressure - ESP - defined as the pressure that would be developed by a fan operating at standard air density instead of the actual air density.
ESP = dp act ρ std / ρ act (4)
ESP = Equivalent Static Pressure (Pa)
dp act = actual pressure (Pa)
ρ std = standard density of air (kg/m 3 )
ρ act = actual density of air (kg/m 3 )
ESP can be useful when selecting fans from published data based on standard conditions.
Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.
Calculate length and speed of belt and belt gearing.
Fan classification established by AMCA.
Pressure, head, air flow volume and fan capacity diagrams.
AHP - Air Horse Power and BHP - Brake Horse Power.
Guide to troubleshooting fan problems.
Turbo machines affinity laws can be used to calculate volume capacity, head or power consumption in centrifugal pumps when changing speed or wheel diameters.
The definition of STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure.
Centrifugal, axial and propeller fans and their capacity ranges.
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