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Agitator Impeller Power & Motor Sizing Calculator engineering
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Agitator Impeller Power & Motor Sizing Calculator

Calculate mixing tank impeller power draw (HP & kW), impeller Reynolds number, turbulent Power Number (Np), and required motor nameplate horsepower.

Impeller & Tank Geometry

Fluid Properties & Baffle Setup

1.0 = water (8.34 lb/gal = 62.4 lb/ft³).

Agitator Power & Sizing

Impeller Shaft Power Draw
-- HP
-- kW mechanical
Recommended Motor
-- HP
Standard NEMA Size
Specific Power
-- HP/1k gal
-- kW/m³
Impeller Reynolds No. (Re): --
Flow Regime: --
Impeller Tip Speed: -- ft/min
Power draw scales with the 5th power of impeller diameter (D⁵) and 3rd power of speed (N³); slight diameter or speed increases rapidly multiply motor load.

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Frequently Asked Questions

Why does impeller power scale to the 5th power of diameter (D⁵)?

The power required by an impeller follows dimensional analysis: P = Np * ρ * N³ * D⁵. Because of the 5th-power sensitivity, doubling impeller diameter at constant RPM increases power consumption by a massive factor of 32 (2⁵ = 32).

Why are tank wall baffles required in high-intensity mixing?

Without baffles, rotating impellers create a solid-body swirl and deep central surface air vortex, which causes fluid stratification, severe shaft vibration, and poor top-to-bottom blending. Four standard vertical wall baffles (width = T/12) break the swirl and convert rotational kinetic energy into vigorous vertical top-to-bottom circulation loops.

What is typical specific power (HP / 1,000 gal) for industrial mixing duties?

Mild liquid blending and storage: 0.5 to 1.5 HP/1,000 gal. Thorough blending and heat transfer: 2.0 to 4.0 HP/1,000 gal. Solid suspension and gas dispersion: 5.0 to 12.0 HP/1,000 gal. Intense high-shear emulsification: 15.0+ HP/1,000 gal.