Chapter

Monitoring and Control of Mixing Operations

DOI: 10.1002/9781444312928.ch7 In book: Food Mixing, pp.107 - 124
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    ABSTRACT: The main objective of this study is to counterpart numerical model and experimental studies for rotating flows associated with dough kneading, and validate the flow patterns generated. The flows considered are in a complex domain setting. Two types of cylindrical vessels are studied at various rotational speeds; one with one stirrer and a second with two. Laser Doppler anemometry is used to obtain the velocity vectors associated with the flow fields. Close agreement is obtained between numerical and experimental flow fields and the magnitudes of velocity vectors. Both sets of results show maximum shear-rates outside the stirring rods. The rate-of-work done also peaks in this region and this is an important quantity to dictate optimal mixer design.
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    ABSTRACT: Stirred vessels are being used not only in chemical processes for simple contacting or blending operations, but also in novel configurations and processes, as in mineral processing and/or wastewater treatment, with specific requirements, like low shear or regions in the vessel with high and low turbulence levels. The techniques that are available for the study of the flow patterns induced by the various types of agitators, e.g., classical pressure or velocity measurements with Pitot tubes or hot-wire anemometers, and novel ones like laser Doppler velocimetry, laser-induced fluorescence and particle image velocimetry are reviewed and their usefulness for particular situations is discussed.
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