Numerical simulation of a 3-D gas-solid fluidized bed: Comparison of TFM and CPFD numerical approaches and experimental validation

Abstract

This paper presents the results of a 3-D numerical simulation of a freely bubbling fluidized bed, based on the Eulerian¿Lagrangian approach, using the software Barracuda (CPFD-Barracuda). The main results obtained were assessed in terms of frequency analysis, bubble pierced length, bubble size, bubble passage frequency and bubble velocity. The results obtained were also compared with experimental data obtained in a 3-D fluidized bed using pressure and optical probes, and with the numerical results using the more common Eulerian-Eulerian approach, implemented in the commercial software Fluent (TFM-Fluent). The results show that CPFD-Barracuda satisfactorily predicts the global behaviour of bubbling beds with a low computational cost, although it computes smaller bubble sizes and lower bubble velocities than TFM-Fluent and experiments. Additionally, the spectra of pressure and particle volume fraction obtained with CPFD-Barracuda resemble those from the experiments and the TFM-Fluent simulations, but with a larger contribution of lower frequencies. The peaks of the pressure spectra from CPFD-Barracuda are close to those from the experiments and the TFM-Fluent simulations, whereas those in the solid volume spectra seem to be underestimated by CPFD-Barracuda. The results also indicate that the particle fraction threshold value chosen to distinguish bubbles contours notably influences the results of the bubble characteristics, especially for TFM-Fluent, whereas CPFD-Barracuda is less sensitive to this threshold value.