The Science of Stirring: A Deep Dive into Agitator Design Calculations
Manufacturers need you to choose the correct motor and impeller, so they publish "Engineering Guides." These are practical and verified by field data.
For turbulent: ( t_b = 5.2 \cdot \left(\fracTD\right)^2 \cdot N^-1 )
Viscosity remains constant regardless of shear rate (e.g., water, mineral oils). agitator design calculation pdf download verified
Agitators (mixers) are used in chemical, pharmaceutical, food, and wastewater industries to achieve blending, suspension, dispersion, heat transfer, or mass transfer. Proper design requires calculating power requirements, shaft diameter, impeller speed, torque, and baffle configuration.
[ N_q = \fracQN D^3 ] Typical Nq: 0.7–0.8 (axial flow), 0.5–0.6 (radial flow). Bulk fluid velocity = Q / cross-sectional tank area.
Parallel shaft or right-angle helical units designed for high shock loads. The Science of Stirring: A Deep Dive into
The heart of any agitator design calculation is the determination of required power. This is universally accomplished through the , also known as the Newton Number (Ne). The power number is a dimensionless quantity that characterizes the power consumption of a specific impeller geometry and is a function of the impeller Reynolds number and Froude number.
Turnovers per minute match process requirements; tip speed remains within safe limits for shear-sensitive fluids. Mechanical Checklist: Shaft operating speed is outside the
cap P equals cap N sub p center dot rho center dot cap N cubed center dot cap D sub a to the fifth power Shaft Diameter ( : Based on the equivalent bending moment ( cap M sub e m end-sub Parallel shaft or right-angle helical units designed for
The mixing Reynolds number classifies the flow regime inside the vessel. It is calculated using the following formula:
Designing to code is not optional; it is fundamental to safety and reliability. A significant Chinese standard is the for Mechanical Stirring Equipment, which specifies design, manufacturing, inspection, and acceptance requirements for chemical and petrochemical plants.
of the tank diameter. Baffles convert swirling tangential flow into productive axial and radial turnover, preventing vortex formation. Positioned at
for axial/radial turbines. High-viscosity anchors feature a ratio of The standard benchmark is . Tall tanks (
Fluid characteristics determine the amount of energy required to achieve the desired mixing outcome. ) and Dynamic Viscosity (