Estimating Power Consumption for Stirred Reactors  

Estimating Power Consumption for Stirred Reactors  

One of the common tasks faced by users of our Amar stirred reactors is estimating power consumptions. Typically, during scale up validation is performed to make sure industrial scale reactors will be correctly sized based on data accumulated during lab trials. Of course, a good vendor will have extensive correlations to estimate power consumption for their own equipment but the section below gives some pointers about how power consumption can be estimated on the basis of extensive chemical engineering literature on mixing processes.

 

Typically, a handbook such as “The Handbook of Industrial Mixing” by Paul and Kresta (Wiley 2004)" should be consulted and Refer Fig.6-14 for excerpts some useful information from this handbook. (Credit due to the original authors! )

 

A graph such as in the Fig.6-14 allows users to estimate the Power Number (Np on the y axis) as a function of Reynolds number(Re). For high Re the power numbers are typically constant but do vary based on the impeller design. Once the user has a good estimate of the power number based on the relationship of the power number with basic known quantities such as density, RPM, and impeller diameter(see formula in Fig.6-15)

When using other impeller shapes a table of the form (Refer Table - 6-4) gives a good empirical estimate of the Power Number that will be encountered.

Note that these are typically valid only in the Turbulent Regime at large Re. To know more about it, Read “The Handbook of Industrial Mixing” by Paul and Kresta (Wiley 2004)".