Power Calculation For Agitator

Agitator Power Number Formula:

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

Power Number (N_p):

dimensionless

Density (ρ):

kg/m³

Rotational Speed (N):

rev/s

Impeller Diameter (D):

Power (P):

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1. What is the Agitator Power Number Formula?

The Agitator Power Number Formula calculates the power required to operate an agitator or mixer in fluid systems. It relates power consumption to fluid properties and impeller characteristics, providing essential data for equipment sizing and energy efficiency analysis.

2. How Does the Calculator Work?

The calculator uses the agitator power formula:

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

Where:

\( P \) — Power (W)
\( N_p \) — Power number (dimensionless)
\( \rho \) — Density (kg/m³)
\( N \) — Rotational speed (rev/s)
\( D \) — Impeller diameter (m)

Explanation: The formula demonstrates that power consumption is highly dependent on impeller diameter (to the 5th power) and rotational speed (to the 3rd power), making these the most critical design parameters.

3. Importance of Agitator Power Calculation

Details: Accurate power calculation is essential for proper motor selection, energy consumption estimation, process optimization, and ensuring adequate mixing performance in chemical, pharmaceutical, and food processing industries.

4. Using the Calculator

Tips: Enter power number (typically 0.2-5 for most impellers), 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: The power number is a dimensionless parameter that characterizes the resistance of an impeller to rotation in a fluid. It depends on impeller type, geometry, and flow regime.

Q2: How do I determine the power number for my impeller?
A: Power numbers are typically obtained from manufacturer specifications, empirical correlations, or experimental data. Common values range from 0.3 for hydrofoils to 5.0 for flat blade turbines.

Q3: Why is diameter raised to the 5th power?
A: The D⁵ dependence comes from the relationship between torque and power. Torque scales with D⁵ while power is torque times angular velocity, making diameter the most influential parameter.

Q4: What are typical power requirements for industrial agitators?
A: Power requirements vary widely from 0.1 kW for laboratory mixers to over 100 kW for large industrial vessels, depending on viscosity, density, and mixing intensity required.

Q5: Does this formula account for non-Newtonian fluids?
A: The basic formula assumes Newtonian fluids. For non-Newtonian fluids, additional corrections for apparent viscosity and flow behavior index may be required.