Investigation of Gas-Solid Flow Dynamics and Heat Transfer in Fluidized Beds by Using DEM-LES Coupling Approach

Bubbling and turbulent fluidization are two typical fluidization regimes in fluidized bedsFluidized bed . Under the Eulerian-Lagrangian framework, the heat transferHeat transfer properties in a bubbling fluidized bedFluidized bed (BFB) and gas-solid behaviors in a three-dimensional (3-D) circulating fluidized bedFluidized bed (CFB) are investigated respectively by using Discrete Element Method-Large-eddy Simulation (DEM-LESDiscrete element method-large-eddy simulation ) coupling approach. The gas behavior is resolved at computational grid level and the solid behavior is handled at particle-scale level, moreover, inter-particle and inter-phase heat transferHeat transfer are involved. Results show that the tube bundles make the solid distribution more uniform. Staggered tube bundle BFB achieves higher heat transferHeat transfer performance. In the CFB, solid internal circulations are observed in the riser. Moreover, the inventories in six standpipes differ even though the geometry of the apparatus is symmetric. The solid back-mixing occurs mainly in the four corners of the riser. In each external circulating system, pressure drop forming between the inlet of riser and the surface of packed beds in standpipes becomes the driven force for solid circulations in the closed loop. In summary, all these crucial mechanisms shed light on the design, operation and scale-up of fluidized bedsfluidized bed in practical engineering fields.