Higher order discretization methods for the numerical simulation of fluidized beds
Numerical models of fluidized beds based on the multiphase mass and momentum balance equations for gas and solids phases continue to be developed by several groups of researchers around the world. It has been demonstrated that the same set of equations is able to describe a wide range of fluidization conditions, ranging from bubbling to circulating fluidized beds. The results of bubbling bed simulations, plots of void fraction distribution, show the formation and propagation of high void fraction regions, called bubbles. This study shows that these problems are numerical artifacts of using first order accurate discretization schemes and coarse grids and are not due to a fundamental difficulty with the theory. This study was motivated by the observation that the shape of the gas hold up profile described by Sokolichin et al. is similar to that of the shape of bubbles in a fluidized bed. Second-order accurate discretization schemes were included in a multiphase flow model of fluidized beds called MFIX. It is shown here that the bubble shape predicted with a second order accurate scheme is rounded. The simulations were conducted for long durations (5 s) and the results did not show the fountain formation at the bed surface. It appears that the fountain formation is caused by coarse grids and low physical viscosity of the solids phase.
- Research Organization:
- EG and G Technical Services of West Virginia, Inc., Morgantown, WV (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Fossil Energy, Washington, DC (United States)
- OSTI ID:
- 650122
- Report Number(s):
- DOE/FETC/C-98/7305; CONF-971113-; ON: DE98051221; NC: NONE; TRN: AHC2DT04%%33
- Resource Relation:
- Conference: Annual meeting of the American Institute of Chemical Engineers (AIChE), Los Angeles, CA (United States), 16-21 Nov 1997; Other Information: PBD: Jan 1997
- Country of Publication:
- United States
- Language:
- English
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