Recently “inherited” an older 20"(?) box fan. It has 3 larger (surface area) metal blades. My newer 20" box fan has 5 smaller (surface area) plastic blades. Got me thinking… if the motors are running at the same RPMs is there/would there be any difference in the amount or speed of air being moved between the 2 fans because of the difference in the size or number of blades.
Depends on the blades and how much power the motor produces. The speed of rotation, shape and angle of the blades makes a difference for a particular motor power. They probably maximized the volume and speed of air movement for the motor and blade type used but the volume and speed of the air flow can be quite different between the two fans still.
From what I understand, it’s the total surface area of the blades that determines the volume of air moved, no matter how many blades it’s spread across.
A 5-blade fan typically moves more air than a 3-blade fan at the same RPM.