Agitator Sizing Calculation

Agitator Power Equation:

\[ P = N_p \times \rho \times N^3 \times D^5 \]

Power Number (N_p):

Density (ρ):

kg/m³

Rotational Speed (N):

rps

Impeller Diameter (D):

Agitator Power (P):

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1. What is Agitator Sizing Calculation?

Agitator sizing calculation determines the power required for mixing operations in industrial processes. The calculation considers fluid properties, impeller characteristics, and operating conditions to ensure proper mixing efficiency and equipment sizing.

2. How Does the Calculator Work?

The calculator uses the agitator power equation:

\[ P = N_p \times \rho \times N^3 \times D^5 \]

Where:

\( P \) — Agitator power (W)
\( N_p \) — Power number (dimensionless)
\( \rho \) — Fluid density (kg/m³)
\( N \) — Rotational speed (rps)
\( D \) — Impeller diameter (m)

Explanation: The power number depends on impeller type and flow regime (laminar, transitional, or turbulent), while the equation accounts for the strong dependence of power on impeller diameter and rotational speed.

3. Importance of Agitator Power Calculation

Details: Proper agitator sizing ensures efficient mixing, prevents under-mixing or over-mixing, optimizes energy consumption, and ensures equipment reliability and process consistency in chemical, pharmaceutical, and food industries.

4. Using the Calculator

Tips: Enter power number based on impeller type and Reynolds number, fluid density in kg/m³, rotational speed in revolutions per second, and impeller diameter in meters. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is the power number (N_p)?
A: Power number is a dimensionless parameter that depends on impeller geometry and flow regime. Typical values range from 0.3 to 5 for common impellers.

Q2: How does Reynolds number affect power calculation?
A: In laminar flow (Re < 10), power number is inversely proportional to Reynolds number. In turbulent flow (Re > 10,000), power number becomes constant.

Q3: What are typical power number values?
A: Rushton turbine: ~5.0, pitched blade turbine: ~1.3-1.7, marine propeller: ~0.3-0.6, anchor: ~0.3-1.0 depending on Re.

Q4: When should this calculation be used?
A: For new agitator design, equipment selection, process optimization, and troubleshooting mixing problems in various industrial applications.

Q5: Are there limitations to this equation?
A: The equation assumes Newtonian fluids and may need modification for non-Newtonian fluids, complex geometries, or when significant aeration or solids suspension occurs.