# Using airflow to find force

• Trebor0808

#### Trebor0808

Hi,

I am doing an experiment where I am measuring the airflow readings (m/s) of different fans. I then was hoping to use this to work out the force and then from that the power to compare the efficiencies of the different fans. I was wondering if anyone had any suggestions for what equations to use to find the force from the air flow as I haven't found any that are particularly helpful?

Thanks.

Better. Suspend the fan as a simple pendulum and measure the displacement and weight just like in physics lab.

Wikipedia appears to have an equation for thrust...
http://en.wikipedia.org/wiki/Axial_fan_design

Fx = ½ρ (CS2 - CU2)

where
ρ = air density
CS2 = velocity downstream of the fan
CU2 = velocity upstream of the fan

Hi,

I am doing an experiment where I am measuring the airflow readings (m/s) of different fans. I then was hoping to use this to work out the force and then from that the power to compare the efficiencies of the different fans. I was wondering if anyone had any suggestions for what equations to use to find the force from the air flow as I haven't found any that are particularly helpful?

Thanks.
Look at Pitot & Bernoulli

what do you mean by force of an airflow? it does not exist something like that.
If u mean the thrust produced by the fan i quote pendulum approach! :p

The power or force is equal to the change of momentum of the air. The efficiency is how much energy is being used to change the momentum.
Measure accurately velocity in and out and the energy consumption of the fan.