Two-dimensional and three-dimensional computational studies of hydrodynamics in the transition from bubbling to circulating fluidised bed
Armstrong, Lindsay-Marie, Gu, Sai and Luo, Kai H. (2010) Two-dimensional and three-dimensional computational studies of hydrodynamics in the transition from bubbling to circulating fluidised bed. Chemical Engineering Journal, 160, (1), 239-248. (doi:10.1016/j.cej.2010.02.032).
This paper applies two-ﬂuid modelling (TFM) to a two dimensional and three dimensional circulating ﬂuidised bed (CFB). An energy minimisation multiscale based drag model (EMMS) is compared with a classical drag model, namely the Gidaspow model in the light of experimental data from the CFB. The axial particle velocities and the radial volume fraction at diﬀerent heights are considered. The specularity coeﬃcient responsible for the tangential solid velocities at the walls is varied to study the eﬀect on the downﬂow of particles at the wall. The work is further extended to explore the eﬀects of velocity variation on the ﬂow distribution showing the transition from a bubbling to a fast ﬂuidising regime. Furthermore, the diameters of the bubbles observed within the bubbling regime are compared with the Davidson’s bubble diameter model for a range of particle diameters. Varying the specularity coeﬃcient showed that a free slip boundary condition underpredicted the downﬂow of particles at the wall and to add slight roughness to the wall gave a closer representation. The predictions for the 2D and 3D CFB axial velocities were in good agreement with the experimental data but the 2D results slightly overpredicted the core velocity. The transition from a bubbling to a fast ﬂuidising regime as expected occurred once the inlet velocity exceeded the terminal velocity. The equivalent bubble diameter from the simulations agreed well with the calculated bubble diameter from the model.
|Keywords:||cfd, hydrodynamics, circulating fluidised bed, eulerian, emms|
|Subjects:||T Technology > TP Chemical technology
T Technology > TA Engineering (General). Civil engineering (General)
|Divisions:||University Structure - Pre August 2011 > School of Engineering Sciences
|Date Deposited:||04 Mar 2010|
|Last Modified:||28 Mar 2014 15:24|
Collaborative Research in Energy with South Africa:Scale-up modelling to answer Pyrolysis Challenge
Funded by: EPSRC (EP/G034281/1)
Led by: Sai GU
1 November 2009 to 30 April 2013
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