Gas-solid fluidized bed hydrodynamics is an advanced field of research that examines the dynamics of gas and solid particles in fluidized bed systems. Fluidized beds have found extensive applications in a range of industrial processes, such as chemical reactions, heat transfer, drying, and combustion, owing to their exceptional mixing, heat transfer, and mass transfer properties. A deep understanding of the hydrodynamics of gas-solid fluidized beds is crucial to maximize their performance and create effective processes.

The present problem aims to validate Figure 9 of the paper entitled “Experimental and computational study of gas-solid fluidized bed hydrodynamics [1] ”. So, the simulation is performed using ANSYS Fluent software, and the results are compared with the experimental data.

• Reference [1]: Taghipour, Fariborz, Naoko Ellis, and Clayton Wong. “Experimental and computational study of gas–solid fluidized bed hydrodynamics.” Chemical engineering science24 (2005): 6857-6867.

Figure 1: Comparison of experiment and simulated bubbles for three drag models [1]

Simulation Process

Figure 2 shows the schematic of a 2D fluidized bed given in the paper. It is designed using ANSYS Design Modeler software. After that, a structured quad grid is produced over the computational domain with the help of ANSYS Meshing. The methodology asks for the activation of Eulerian Multiphase module in which gas and particle beads are modeled. However, the solid bed requires granular assumption and its related properties, including granular viscosity, solid pressure, granular temperature, etc., are taken according to the reference paper.

Figure 1- 2D schematic of fluidized bed

Post-processing

The time-averaged cross-sectional voidage profile shows excellent agreement between numerical and experimental findings, especially in defining the essential transition zones of the fluidized bed. The validation chart outlines three distinct regions: a dense lower zone (h/H < 0.2) characterized by a voidage of around 0.4, a transitional region (0.2 < h/H < 0.6) in which voidage gradually increases, and a dilute upper region (h/H > 0.6) nearing maximum voidage values of 0.8-0.9. The numerical simulation accurately forecasts these transitions, with maximum errors from experimental data not exceeding 10%. This precision confirms both the selected Eulerian-Eulerian methodology and the applied granular flow parameters, such as particle-particle interaction coefficients and granular temperature models. The robust correlation between simulation and experimental results, especially in the difficult transition zone, validates the model’s ability to capture the intricate physics of gas-solid interactions.

Figure 3: Validation data chart of Gas-solid Fluidized Bed Hydrodynamics – Experimental Paper Validation

The animation illustrates the dynamic features of bed hydrodynamics, highlighting specific fluidization regimes and bubble production patterns. As gas initially infiltrates the particle bed, little bubbles form near the distributor plate, expanding and combining as they rise. The particle circulation patterns exhibit distinct characteristics of bubbling fluidization, with dense areas along the walls where particles drop and core regions where bubble-induced particle movement occurs. The bed expansion ratio varies between 1.5 and 1.7 times the initial bed height, with periodic eruptions at the bed surface resulting in particle ejection into the freeboard zone. The dynamic behaviors illustrated in the video correspond with conventional fluidization theory and exhibit the model’s capacity to forecast both time-averaged characteristics and transient events. The existence of coherent bubble formations and their developmental patterns offers qualitative confirmation of the numerical method, augmenting the quantitative validation demonstrated in the voidage profiles.

Figure 4: Solid volume fraction