Reactor Agitator Power Calculation

Agitator Power Equation:

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

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 the Agitator Power Equation?

The agitator power equation calculates the power required to operate a mechanical agitator in a reactor or mixing vessel. It is based on the power number concept which relates power consumption to fluid properties and agitator geometry.

2. How Does the Calculator Work?

The calculator uses the agitator power equation:

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

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 agitator type and flow regime (laminar, transitional, or turbulent). Typical values range from 0.3 to 6.0 depending on impeller design.

3. Importance of Agitator Power Calculation

Details: Accurate power calculation is essential for proper motor sizing, energy efficiency optimization, and ensuring adequate mixing performance in chemical reactors and process vessels.

4. Using the Calculator

Tips: Enter power number (dimensionless), fluid density in kg/m³, rotational speed in revolutions per second (rps), 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 power consumption of an agitator. It depends on impeller type, geometry, and flow regime.

Q2: How do I determine the power number for my agitator?
A: Power numbers are typically obtained from manufacturer specifications, experimental data, or correlations specific to impeller type and Reynolds number.

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

Q4: Does this equation work for all flow regimes?
A: The equation is valid for turbulent flow. For laminar and transitional flow, the power number becomes a function of Reynolds number.

Q5: What factors affect agitator power consumption?
A: Fluid viscosity, density, impeller design, rotational speed, vessel geometry, and presence of baffles all influence power requirements.