A critical validation study on CPFD model in simulating gas–solid bubbling fluidized beds

• A critical validation study on CPFD model in simulating bubbling fluidized beds
• Accurate experimental data and TFM simulation results used as references
• Some advantages are discerned and proved again.
• An inherent disadvantage was identified.
• Model improvements still needed to improve solids stress and solids–wall interactions

CPFD model is a new Eulerian–Lagrangian CFD approach which allows simulating large-scale industrial multiphase flow systems in affordable time by adopting the particle parceling algorithm and MP-PIC method. In this study, a critical validation study was carried out to examine its performance in simulating gas–solid bubbling fluidized beds. The pseudo-2D fluidized bed of Hernández-Jiménez et al. [27] was simulated by a recent version of CPFD model, i.e. Barracuda 15.1. The accurate experimental data of bubble properties and solid velocity measured by Digital Image Analysis (DIA) and Particle Image Velocimetry (PIV) techniques in their study [27] were used to examine the quality of the simulation results. The simulated results by a Two-Fluid Model (TFM) model [27] were also used as a reference to demonstrate the strength and weakness of this model. The results show that CPFD model can obtain better profiles of solids velocity, but it cannot correctly simulate the bubble coalescence phenomenon in bubbling fluidized beds, which results in a flat lateral profile of bubble possibility deviating considerably from the experimental fact. The currently available adjusting measures, except for the near-wall local mesh refinement, have little effect in improving the simulation results. A bug in the initial solids packing by the current version of Barracuda was identified. Loss of solid mass is found in simulating small systems of relatively large particles using small real particle numbers in parcel. Suggestions were proposed to avoid this mass-imbalance problem and for future program modification. More efforts are still needed to improve the algorithms of solid stress model and solid–wall interactions to make CPFD model more qualified in simulating bubbling fluidized beds.

A critical validation study of CPFD model was carried on simulating bubbling gas–solid fluidized bed. A previous study on a pseudo-2D fluidized bed with accurate experimental data and TFM modeling results were used to identify its strength and weakness. Although some advantages of the CPFD model were discerned or proved again, an inherent disadvantage was also identified, i.e. its incapability in simulating the right bubble coalescence phenomenon in bubbling fluidized beds. These results can be used as good references for other users and future model improvements.Figure optionsDownload as PowerPoint slide