Stirred-Tank Mixing Power
Stirred-Tank Mixing Power
The power an impeller draws scales steeply with its speed and size, captured by the dimensionless power number.
The power is P = N_p·ρ·N³·D⁵. where N_p is the power number, ρ the density, N the speed and D the impeller diameter.
Inputs
N_p := 5=5
rho := 1000 kg/m^3=1000 kg/m^3
N := 4 Hz=4 Hz
D := 0.3 m=300 mm
Apply the mixing-power correlation.
P := N_p·rho·N^3·D^5=777.6 W
Results
Power rises with the cube of speed and the fifth power of diameter, so a small impeller change drastically alters the motor load — the key scale-up constraint.
Assumptions & limitations
- Turbulent regime (constant power number).
- Newtonian fluid.
- Speed in revolutions per second.