The generality of the standard 2D TFM approach in predicting bubbling fluidized bed hydrodynamics

Hydrodynamic simulations of a pseudo-2D bubbling fluidized bed were carried out and compared to experiments conducted over a wide range of flow conditions. The primary purpose of this study was to assess the generality of the standard 2D Two Fluid Model (TFM) closed by the Kinetic Theory of Granular Flows (KTGF) which is regularly used in the literature to simulate bubbling fluidized beds. Comparisons of the bed expansion ratio over wide ranges of fluidization velocity, bed loading and particle size showed systematic differences between simulations and experiments, indicating that the generality of this modelling approach is questionable. More detailed flow velocity measurements collected via Particle Image Velocimetry (PIV) showed that the model greatly over-predicts flow velocities in the bed. Subsequent 3D simulations showed this over-prediction to be the result of 2D simulations neglecting the wall friction at the front and back walls of the pseudo-2D bed.

Graphical abstractThe performance of the 2D TFM approach was evaluated over a range of fluidization velocities, bed loadings and particle sizes. The model accurately predicted changes in the bed expansion as the fluidization velocity was increased (shown here) despite large over-predictions of the solids velocity. Systematic differences between simulation and experiment were observed for the remaining two variables.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The generality of the 2D TFM approach was evaluated in this study. ► Simulation results were compared to dedicated experiments. ► Comparisons were carried out over a wide range of flow conditions. ► Predictions of the bed expansion showed systematic differences with experiments. ► Large solids velocity over-predictions resulted from neglected 3D wall friction.