Particle-Scale Investigation of the Hydrodynamics and Tube Erosion Property in a Three-Dimensional (3-D) Bubbling Fluidized Bed with Immersed Tubes

Abstract

Particle-scale study of the gas–solid hydrodynamics and the tube erosion in a 3-D bubbling fluidized bed with a tube bundle is conducted in the framework of computational fluid dynamics coupled with the discrete element method. General gas–solid flow behaviors are investigated and the time-averaged properties are obtained to explore the influence of tube configuration on the bed hydrodynamics. Moreover, the erosion patterns of immersed tubes locating in the different regions of system are analyzed. The effect of tube configuration on the erosion property is considered. The results show that the presence of the tube bundle limits the bubble diameter and results in homogeneous distribution of the bubble phase in the tube region. Moreover, inserting the tube bundle into the bed reduces the vertical velocity of the solid phase but results in a uniformly horizontal distribution of its concentration. The vertical intensity of solid dispersion is several times that of the lateral one, and the insertion of tube bundle enhances the solid mixing procedure and enlarges the solid dispersion intensities in both the vertical and lateral directions. Different erosion patterns appear on the immersed tubes locating in different regions of the bed. The intrinsic mechanism behind the erosion distribution can be identified from the solid flux distribution near the tubes.

Coupling CFD-DEM with dynamic meshing: A new approach for fluid-structure interaction in particle-fluid flows

“…Different approaches have been used to treat the stationary boundary of the tube in CFD calculation either using staircase approximation on a Cartesian grid [20,21] or accurately representing the boundary shape using body-fitted unstructured mesh [22,23]. Considerable efforts have been devoted to various aspects of the fluidized bed, including heat transfer [21,24,25], bubble hydrodynamics [20,26] and erosion of the tube surface [27]. However, the capability of CFD-DEM methods to tackle FSI problems in particle-fluid flow is lacking, especially when the fluid field is described by a continuous mesh-based method, such as Finite Volume Method (FVM) or Finite Difference Method (FDM).…”

Improvement of hydrodynamics and heat transfer in biomass fluidized bed combustor with immersed tubes using CFD-DEM

“…The solid particles exhibit vigorous upward motion primarily in the central region of the bed, particularly in the dome and wake of the bubble phase. Once the bubble phase erupts at the top region, the particles disperse into the free domain of the bed, causing intense downward flow near the bed wall [121].…”