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New Methods for Flow Regime Identification in Bubble Columns and Fluidized Beds

Nedeltchev, S.


New methods for flow regime identification were developed and applied to photon count time series measured in a bubble column (0.162 m in ID) and fluidized bed (0.438 m in ID). The signals in the bubble column (operated with an air-therminol system) were measured by means of Computed Tomography (CT), whereas the data in the fluidized bed (operated with an air-polyethylene system) were recorded by means of Nuclear Gauge Densitometry (NGD). The hidden information in the time series was extracted by means of two new parameters: entropy (bit/s) and information entropy (bit). Both of them were calculated on the basis of multiple reconstructions of the time series. In the case of the bubble column, the well-pronounced local minima were used for identification of three transition velocities (0.04, 0.08 and 0.13 m/s). They distinguished the boundaries of the bubbly flow, transition and churn-turbulent flow regimes. In the case of the fluidized bed, the minimum fluidization velocity (0.086 m/s) and minimum bubbling velocity (0.12 m/s) were also identified on the basis of the well-pronounced local minima in the profiles of the new parameters. They distinguished the boundaries of both the transition and bubbling fluidization regimes.

Keywords: Flow regime identification; Bubble column; Fluidized bed; Transition velocities; Entropy; Information entropy


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