Chemical Tank Agitator Calculation

Agitator Power Number Formula:

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

Power Number (N_p):

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 a mechanical agitator in a chemical tank. It relates power consumption to fluid properties and agitator geometry, helping engineers design efficient mixing systems.

2. How Does the Calculator Work?

The calculator uses the agitator power formula:

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

Where:

\( P \) — Power (watts)
\( N_p \) — Power number (dimensionless)
\( \rho \) — Fluid density (kg/m³)
\( N \) — Rotational speed (revolutions per second)
\( D \) — Impeller diameter (meters)

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

3. Importance of Agitator Power Calculation

Details: Accurate power calculation ensures proper motor sizing, prevents equipment failure, optimizes energy consumption, and ensures adequate mixing for chemical processes.

4. Using the Calculator

Tips: Enter power number (typically 0.2-5 for common 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 depends on impeller type, geometry, and flow regime (Reynolds number).

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 for specific impeller types.

Q3: What are typical power number values?
A: Radial flow impellers: 3-5, axial flow impellers: 0.2-1.0, depending on specific design and Reynolds number.

Q4: Does this formula account for non-Newtonian fluids?
A: The basic formula assumes Newtonian fluids. For non-Newtonian fluids, additional corrections for apparent viscosity may be needed.

Q5: What safety factors should be applied?
A: Typically 10-20% safety margin is added to calculated power to account for startup conditions, fluid property variations, and equipment aging.