How to Calculate Impeller Size

Impeller Diameter Formula:

\[ D = \left( \frac{P}{\rho N^3 K} \right)^{\frac{1}{5}} \]

Power (P):

Density (ρ):

kg/m³

Rotational Speed (N):

s⁻¹

Constant (K):

Impeller Diameter (D):

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1. What is Impeller Diameter Calculation?

The impeller diameter calculation determines the optimal size of an impeller based on power requirements, fluid properties, and operating conditions. This is crucial for efficient pump and mixer design in various industrial applications.

2. How Does the Calculator Work?

The calculator uses the impeller diameter formula:

\[ D = \left( \frac{P}{\rho N^3 K} \right)^{\frac{1}{5}} \]

Where:

\( D \) — Impeller diameter (m)
\( P \) — Power input (W)
\( \rho \) — Fluid density (kg/m³)
\( N \) — Rotational speed (s⁻¹)
\( K \) — Power constant (dimensionless)

Explanation: The formula relates impeller diameter to power consumption, accounting for fluid density and rotational speed through dimensional analysis and power number relationships.

3. Importance of Impeller Sizing

Details: Proper impeller sizing ensures optimal mixing efficiency, prevents cavitation, reduces energy consumption, and extends equipment lifespan. Incorrect sizing can lead to poor performance and mechanical failures.

4. Using the Calculator

Tips: Enter power in watts, density in kg/m³, rotational speed in revolutions per second, and the appropriate power constant. All values must be positive and non-zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the power constant K?
A: The power constant depends on impeller type and flow regime. Typical values range from 0.2 to 5.0 for different impeller designs and Reynolds numbers.

Q2: How does fluid viscosity affect the calculation?
A: Viscosity influences the power constant K. Higher viscosity fluids generally require higher power constants and may need different impeller designs.

Q3: What are typical impeller diameter ranges?
A: Impeller diameters typically range from 0.1 to 3 meters depending on application, with smaller diameters for laboratory mixers and larger for industrial processes.

Q4: Can this formula be used for all impeller types?
A: This formula is most accurate for standard radial and axial flow impellers. Specialized impellers may require modified formulas or empirical correlations.

Q5: How important is rotational speed in the calculation?
A: Rotational speed has a significant impact as it appears cubed in the denominator, making it one of the most sensitive parameters in the calculation.