Development and verification of coarse‐grain CFD‐DEM for nonspherical particles in a gas–solid fluidized bed

Abstract

Computational fluid dynamics coupled with discrete element method (CFD‐DEM) has been widely used to understand the complicated fundamentals inside gas–solid fluidized beds. To realize large‐scale simulations, CFD‐DEM integrated with coarse‐grain model (CG CFD‐DEM) provides a feasible solution, and has led to a recent upsurge of interest. However, when dealing with large‐scale simulations involving irregular‐shaped particles such as biomass particles featuring elongated shapes, current CG models cannot function as normal because they are all developed for spherical particles. To address this issue, a CG CFD‐DEM for nonspherical particles is proposed in this study, and the morphology of particles is characterized by the super‐ellipsoid model. The effectiveness and accuracy of CG CFD‐DEM for nonspherical particles are comprehensively evaluated by comparing the hydrodynamic behaviors with the results predicted by traditional CFD‐DEM in a gas–solid fluidized bed. It is demonstrated that the proposed model can accurately model gas–solid flow containing nonspherical particles, merely the particle dynamics are somewhat lost due to the scaleup of particle size. Finally, the calculation efficiency of CG CFD‐DEM is assessed, and the results show that CG CFD‐DEM can largely reduce computational costs mainly by improving the calculation efficiency of DEM. In general, the proposed CG CFD‐DEM for nonspherical particles strikes a good balance between efficiency and accuracy, and has shown its prospect as a high‐efficiency alternative to traditional CFD‐DEM for engineering applications involving nonspherical particles.

Efficiency Analysis of the Discrete Element Method Model in Gas‐Fluidized Beds

“…There has been a great deal of reliance on Eulerian-Eulerian methods in the past, specifically the two-fluid model in fluidized-bed studies [11][12][13]. The CFD-discrete element method (CFD-DEM) exhibits more advantages for predicting binary solid mixing in a fluidized bed than the Eulerian-Lagrangian methods and can provide critical information at the level of individual particles, such as particle trajectory, forces acting on individual particles, and the property changes of particles [14,15].…”

Numerical investigation of the reactive gas–solid characteristics in biomass fast pyrolysis of conical spouted reactor equipped with draft tube

“…A popular method for simulating gas-solid multiphase flow is the CFD coupled with discrete element method (CFD-DEM) approach, which is a highfidelity modeling regime to resolve solid motion and collision. 18 Via this approach, numerous reports have been carried out to investigate biomass fast pyrolysis. [19][20][21] However, the CFD-DEM fails to simulate multiphase flow in large-scale apparatus because of prohibitive computational cost.…”

“…To make up for this deficiency, the Eulerian–Lagrangian framework has been introduced where the fluid phase is still solved as continuum by the Navier–Stokes (N–S) equations while the solid phase is regarded as discrete elements and tracked by the Newton's Law. A popular method for simulating gas–solid multiphase flow is the CFD coupled with discrete element method (CFD‐DEM) approach, which is a high‐fidelity modeling regime to resolve solid motion and collision 18 . Via this approach, numerous reports have been carried out to investigate biomass fast pyrolysis 19–21 .…”

CFD-DEM Fluidized Bed Drying Study Using a Coarse-Graining Technique

“…One of the most extensively researched methods is presented in ref . Subsequently, fluidized beds were studied using this scaling law. − Several other coarse-graining techniques exist; see, for example, refs − . However, based on the review in ref , it is clear that research is mainly focused on bed hydrodynamics, and only a few literature studies reported coarse-graining scaling laws for gas-particle heat and mass transfer.…”