Question

Rushton turbine, impeller diameter = 20 cm. Speed = 200 rpm. Flow rate = 0.2 m\(^3\)/min. Find the Froude number $N_{Fr}$ (round to 2 decimals).

Hint:

Rushton turbine mixing uses $N_{Fr}$ to characterize vortex formation.

Answer 1

Correct Answer: 0.21

Convert units: \[ D = 0.20\ \text{m}, N = \frac{200}{60} = 3.333\ \text{rps} \] Froude number: \[ N_{Fr} = \frac{N^2 D}{g} = \frac{(3.333)^2 \times 0.20}{9.81} \] \[ = \frac{11.11 \times 0.20}{9.81} = \frac{2.222}{9.81} = 0.2266 \] Rounded: \[ \boxed{0.23} \]