Extension Of A Model For The Distribution Of Voidage Around Bubbles In A Fluidized Bed
Author(s)
C. Rautenbach, C. Jayarathna, M. C. Melaaen & B. M. Halvorsen
Abstract
Up to date most models predicting the voidage around bubbles in fluidized beds
assume a simple two-phase flow model. A classic example of a model using this
basic assumption is the Davidson and Harrison bubble model. In more recent
experimental studies it has been shown that there exists a shell of lower voidage
around a bubble in a fluidized bed. Better understanding of these phenomenamight
play a significant role in understanding other very important effects associated with
bubbles in fluidized beds. An example of this might be better understanding the
wake of a bubble rising in a fluidized bed and also to better predict mixing in a
fluidized bed. The amount of contact between the gas and the solids in a gas-solid
fluidized bed is paramount for designing an effective fluidized bed reactor.
In the present study a model describing the voidage distribution in front and
behind a bubble in a fluidized bed was reexamined and extended. The model proposed
by Buyevich et al. used some basic assumptions and previously derived
models to compose the model. In the present study the model is extended to two
dimensions to give a non-uniform particle distribution around the bubble. Thus
voidage distributions all around the bubble could be determined. This new distribution
of the voidage could be used to determine a new form of the bubble surface
and thus a new boundary condition for the fluidized bubble.
The results from the model are compared with simulations carried out at the
TUC in Porsgrunn, Norway. The results are discussed and evaluated.
Keywords
solid fraction, voidage distribution, bubble model, fluidization.
Related Book
Other papers in this volume
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