For multiple impellers, the total process power is the sum of the individual impellers, adjusted for their spacing along the shaft. 4. Mechanical Design and Shaft Integrity
Proper agitator design calculation is crucial for several reasons:
Choose the type (axial vs. radial) and quantity of impellers. Size Motor/Gearbox:
Agitator (mixer) design is a core responsibility for chemical, pharmaceutical, and food process engineers. Getting the right balance between flow, shear, power, and tank geometry can make or break a mixing process. agitator design calculation xls repack
An typically automates these formulas: Agitator Power Requirement: (for turbulent flow) Motor Power Sizing: is efficiency) Mixing Intensity: Calculated as power per unit volume ( ) or tip speed ( 4. How to Use the Agitator Design Calculation Spreadsheet
) to ensure the operating speed is not near the shaft's natural frequency, which would cause destructive vibration.
Nc=602πgδcap N sub c equals the fraction with numerator 60 and denominator 2 pi end-fraction the square root of the fraction with numerator g and denominator delta end-fraction end-root = Acceleration due to gravity ( For multiple impellers, the total process power is
Fluid density, viscosity, tank dimensions, chosen RPM, and impeller type. White (Locked)
Automated calculations for non-Newtonian, high-viscosity fluids (impeller type selection changes based on viscosity). Library of Impellers: Pre-programmed Npcap N sub p and Flow Number ( Nqcap N sub q ) data for standard impellers.
Cells configured with automated IF and VLOOKUP statements to determine NRecap N sub cap R e end-sub radial) and quantity of impellers
A dimensionless constant specific to the impeller type (e.g., turbine, paddle, anchor). (Density): The specific gravity of the liquid. (Rotational Speed): The speed in revolutions per second. cap D sub a (Impeller Diameter):
): Expressed in revolutions per minute (RPM) or revolutions per second (RPS). This dictates the tip speed ( ), which is calculated as:
) does not exceed 70-80% of the shaft's first natural critical frequency ( Nccap N sub c
Shaft diameter sizing, torque, bending moments, critical speed. Reference lookup curves Npcap N sub p curves for different impellers (Rushton, Hydrofoil). Summary of Reference Constants Use these standard turbulent Power Numbers ( Npcap N sub p ) in your database tab for preliminary sizing: Rushton Turbine (6-Flat Blade): (High shear, gas dispersion) Pitched Blade Turbine ( 45∘45 raised to the composed with power ): (Axial flow, macro-blending) Hydrofoil (High-Efficiency Axial): (Low shear, high pumping efficiency)