# Topic: Re: What's the best way to check mixing design?

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You could check many aspects of the mixer design -- some easy, others more difficult.&nbsp; You can check the power requirement, based on impeller type, impeller diameter, rotational speed, fluid density, and viscosity.&nbsp; &nbsp;The power number is a characteristic of the impeller type and geometric dimensions.&nbsp; The power number for a typical 4-blade, 45-degree pitched-blade impeller is 1.37, for a 3-blade hydrofoil the power number is about 0.31, and for a 4-blade, straight-blade (radial flow) impeller use a power number of 3.96.&nbsp; Use one of the two attached power calculations for turbulent power, depending on the units you prefer to use.&nbsp; The motor should be 10% to 20% greater than the calculated impeller power.&nbsp; A correction may be needed if the viscosity results in a Reynolds number less than 20,000.&nbsp;Torque can be calculated from the power and speed of the mixer.&nbsp; Impeller power and speed should be used for the torque to evaluate mixing intensity.&nbsp; Motor power and mixer speed should be used to evaluate the drive torque.&nbsp; Calculations can be made for shaft diameter and natural frequency, see Chapter 21 of the Handbook of Industrial Mixing (Paul, Atiemo-Obeng, and Kresta; John Wiley &amp; Son, 2004.)&nbsp; Other aspects of the mixer selection can be investigated depending on the application with other chapters in the Handbook.
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CALCULATIONS:
Impeller Power Calculation
Impeller Power Calculation_SIReynolds Number Evaluation with DefinitionReynolds Number Evaluation with Metric ConversionTorque Evaluation SI with DefinitionTorque Evaluation with Definition