Abstract
Mechanical mixing can be conducted in few ways. One is unsteady mixing which is used in all cases where it is not recommended to use baffles. In this mixing, the impeller speed is variable over time which causes a higher mixing power demand as compared to steady mixing. In unsteady mixing, also a higher stress around the impeller can be observed as well as the increased axial force in the stirred vessel which results in lower minimum impeller speed in solid-liquid systems. Thus, mixing can be also used in gas-liquid systems allowing to generate a higher relative power demand in relation to the steady mixing as well as higher mass transfer coefficients. Its value, just as for steady mixing, is affected by impeller’s geometry. This chapter analyzes how the shape of impeller’s blade affects the steady and unsteady mixing for impellers with elliptical and hollow unsymmetrical blades. In addition, basic equations describing the torque and impeller speed variations over time are presented together with the maximum and average mixing power equations.
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This work was supported by PUT research grant no. 03/32/DSPB/0702.
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Frankiewicz, S., Woziwodzki, S. (2018). Effect of Blade Shape on Unsteady Mixing of Gas-Liquid Systems. In: Ochowiak, M., Woziwodzki, S., Doligalski, M., Mitkowski, P. (eds) Practical Aspects of Chemical Engineering. Lecture Notes on Multidisciplinary Industrial Engineering. Springer, Cham. https://doi.org/10.1007/978-3-319-73978-6_9
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DOI: https://doi.org/10.1007/978-3-319-73978-6_9
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