Agitator design calculation spreadsheets (XLS) are essential tools in chemical engineering for sizing mixing equipment, determining motor power, and ensuring mechanical integrity. An effective XLS template automates complex, iterative calculations involving fluid dynamics and mechanical stresses. 1. Process Geometry and Fluid Properties
The first section of a design spreadsheet defines the vessel and fluid characteristics. Vessel Geometry: Input the tank diameter ( DTcap D sub cap T ) and liquid height ( ). Standard proportions often suggest an ratio between 0.8 and 1.5. Fluid Properties: Define density ( ) and dynamic viscosity (
). These are critical for calculating dimensionless numbers.
Impeller Selection: Choose the impeller type (e.g., Rushton turbine for radial flow or pitched blade for axial flow) and its diameter ( Dacap D sub a 2. Dimensionless Number Calculations agitator design calculation xls
The spreadsheet must calculate these values to characterize the mixing regime.
Impeller Reynolds Number - an overview | ScienceDirect Topics
The shaft must withstand the torque transmitted from the motor to the impeller. Process Geometry and Fluid Properties The first section
Torque ($\tau$): $$\tau = \fracP2 \cdot \pi \cdot N$$
Shaft Diameter ($d$): Assuming a solid shaft and using the shear stress formula:
$$d = \left( \frac16 \cdot \tau\pi \cdot S_s \right)^1/3$$ Fluid Properties : Define density ( ) and
Where $S_s$ is the allowable shear stress of the shaft material (e.g., Stainless Steel 316 typically $\approx 40-60$ MPa).
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| Formula | Calculation | Result | |---------|-------------|--------| | N (rev/sec) = N_rpm / 60 | =150/60 | 2.5 rps | | Reynolds number, Re = (ρ × N × D²) / μ | =1000×2.5×0.67²/0.001 | 1,122,250 | | Flow regime | If Re<10: laminar; 10<Re<10k: transition; >10k: turbulent | Turbulent |