1

**General Science / Re: How to calculate fan power - formula?**

« **on:**05/05/2018 11:00:03 »

The equation P = ½ρAv

However this only calculates the power transferred to the air. To calculate the fan speed you need to know its efficiency, which is a complicated and nonlinear function of the blade geometry and v. That said, if you assume 100% transfer at the optimum speed for a given fan, then the swept volume per second is Av and each blade sweeps an area A ω times per second where ω is the rotation speed, so you can calculate ω for a fan with n blades.

^{3}is correct. ρ is the density of air, A the area of the fanduct, and v the exhaust speed.However this only calculates the power transferred to the air. To calculate the fan speed you need to know its efficiency, which is a complicated and nonlinear function of the blade geometry and v. That said, if you assume 100% transfer at the optimum speed for a given fan, then the swept volume per second is Av and each blade sweeps an area A ω times per second where ω is the rotation speed, so you can calculate ω for a fan with n blades.

The following users thanked this post: ciniva