Improving the accuracy of two-fluid sub-grid modeling of dense gas-solid fluidized flows

Niaki, Seyed Reza Amini; Mouallem, Joseph; Chavez‐Cussy, Norman; Milioli, Christian C.; Milioli, Fernando Eduardo

doi:10.1016/j.ces.2020.116021

Cited by 9 publications

(4 citation statements)

References 35 publications

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“…Comprehensive descriptions of MFIX can be found elsewhere. [ 41,42 ] A version of MFIX was applied which was modified by including the interparticle friction modelling approach of Berzi and Vescovi [ 37 ] (as implemented by Milioli [ 43 ] and further tested by Niaki et al [ 31 ] ). A typical fluid catalytic cracking particulate was applied in all of the simulations, also following previous literature.…”

Section: Simulation and Filtering Proceduresmentioning

confidence: 99%

“…[27,28] In addition, there were also a number of works where a third marker was accounted for, just by defining sets of markers mostly combining among the above mentioned ones. [27][28][29][30][31] More recently, in addition to inside filter markers, macro-scale related parameters were also included into the correlation analysis by Mouallem et al [22,23] Besides the inside filter parameters, correlation was also established with the domain average solid volume fraction and the domain average gas flow Reynolds number (factors known to define topology in gas-solid fluidized flows). Both of those macro-scale parameters were shown to considerably affect sub-grid filtered data, and should, therefore, be considered as additional independent variables in addition to suitable inside filter parameters.…”

Section: Introductionmentioning

confidence: 99%

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On the effects of the flow macro‐scale over sub‐grid modelling in dense gas–solid fluidized flows

et al. 2022

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Multiscale modelling of gas–particle fluidized flows is frequently approached by means of sub‐grid modelling, which provides constitutive closures for filtered formulations applied to large scale simulations. A widely practiced procedure for the derivation of sub‐grid models consists of filtering over predictions from highly resolved simulations under two‐fluid modelling. The present work is intended as a contribution in this field by providing new supporting evidence for the enhancement of sub‐grid closure models. Most of the efforts in the area have been directed to providing sub‐grid models dependent on meso‐scale filtered effects alone, and under low gas Reynolds number suspension conditions. In this work, macro‐scale conditions are added to the analysis thereby accounting for flow topology, particularly for dense gas–solid fluidized flows. Two macro‐scale variables are considered in the simulations, namely the domain average solid volume fraction and the domain average gas Reynolds number. So, in addition to the usual meso‐scale filtered markers, relevant filtered parameters are also related to those macro‐scale conditions. The filtered parameters of interest here are the effective interphase drag coefficient and filtered and residual stresses in both of the phases. Various domain average solid volume fractions and domain average gas Reynolds numbers were enforced, thereby providing for a variety of macro‐scale dense conditions. It was found that both these macro‐scale parameters considerably affect the meso‐scale and the resulting filtered parameters of dense gas–solid flows, even though this occurs in a milder way when compared to results for dilute flow conditions available in the literature.

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Section: Simulation and Filtering Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the effects of the flow macro‐scale over sub‐grid modelling in dense gas–solid fluidized flows

et al. 2022

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“…Compared with the particle-resolved Eulerian–Lagrangian model, which directly tracks the motion of each particle with high computational cost, , the coarse-grained discrete element method and Eulerian multifluid approach treating both gas and particle phases to be fully interpenetrating continuums have become preferred choices for fluidized bed simulations . When coarse grids are employed in the simulation for bubbling fluidized beds, subgrid models for constitutive closure corrections are required to account for the effect of unresolved inhomogeneous structures. , Among the numerous mesoscale drag models, the filtered method − and the energy-minimization multiscale (EMMS) method − have attracted the most attention. The so-called EMMS bubbling drag model follows a structure-resolved way to calculate the drag coefficient explicitly and thereby calls for reliable estimation of the bubble size within computing cells, which is however closed incorrectly by the empirical correlations for equilibrium bubble diameter in previous studies.…”

Section: Introductionmentioning

confidence: 99%

Machine Learning Assisted Characterization of Local Bubble Properties and Its Coupling with the EMMS Bubbling Drag

Jin,

Hu,

Liu

et al. 2024

Ind. Eng. Chem. Res.

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Empirical correlations for bubble diameter and velocity are incapable of predicting the local bubble behaviors fairly because the impact of local hydrodynamics on bubbles in fluidized beds. Based on image processing, a novel bubble identification method with an adaptive threshold was proposed to distinguish and characterize bubbles in fluidized beds. The information regarding bubble properties and local hydrodynamics can thus be extracted using the big data from highly resolved simulations. Accordingly, the deep neural network was trained to accurately predict local bubble properties, where the inputs were determined by performing correlation analysis and a random forest algorithm. We found Reynolds number, voidage, and relative coordinates are the dominant factors, and a four-variable choice was demonstrated to output satisfactory performance for predicting local bubble diameter and velocity. The model was preliminarily validated by coupling with the EMMS drag into CFD codes, which showed that the accuracy of coarse-grid simulations can be significantly improved.

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“…Further, in high operating voltages, the reaction rates increase, and with a large amount of product water, the cell is prone to flooding phenomenon. 26–33 The flooding in PEM fuel cells increases the transport resistance of the reactants to the active sites causing performance deterioration, energy losses, and reduction in the durability of the materials. 34 Flooding in gas channels of PEMFCs has been studied experimentally and numerically with in-situ and ex-situ visualizations by transparent channels and single/multi-phase one/two/three-dimensional steady-state mathematical models.…”

Section: Introductionmentioning

confidence: 99%

Effect of cathode-side gas flow channels section geometry on the removal process of liquid slug in a proton exchange membrane fuel cell

Abdollahi

Jafarmadar

Jabbary

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part E:

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In low operating temperatures, provided water of Proton-Exchange Membrane Fuel Cells (PEMFCs) is discharged in the state of tiny/large droplets, slugs, and semi-slugs, which strongly depends on the flow channels' characteristics. In this study, the discharge capabilities of channels with different height-to-width aspect ratios are inspected using a transient two-phase numerical simulation. The numerical model includes a segment of the gas channel on the cathode side, and the operating conditions are those related to an actual fuel cell application. Results showed that channels with minimum height could lift the initial slug to the upper part 2.16 times faster and immediately form film flow at the corners. For a fixed width, decreasing channel height from 1.5 mm to 0.5 mm, results in 38.3% faster discharge time and a 62.3% increment in the clearance rate of the gas-diffusion layer. For higher channels, the combined effect of shear stress, gravity, and the adhesive forces of hydrophilic walls cannot lift the initial slug continuously and causes it to rupture, distort, and partially spread over the Gas-diffusion layer (GDL) surface, which leads to mass transport limitation for the cell. Furthermore, when the channel width decreases from 1.5 mm to 0.5 mm for a fixed height, the initial slug leaves the computational domain 51.1% faster. Overall, it was found that the smaller dimensions for height and width show superior cell performance regarding faster water removal, clearer GDL surface, and more uniform flow distribution over the entire electrochemical active area. A channel with a cross-section dimension of 0.5 mm × 0.5 mm is suggested as the best channel design among the analyzed cases for maximum efficiency for the cathode-side flow fields of a PEMFC.

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Improving the accuracy of two-fluid sub-grid modeling of dense gas-solid fluidized flows

Cited by 9 publications

References 35 publications

On the effects of the flow macro‐scale over sub‐grid modelling in dense gas–solid fluidized flows

On the effects of the flow macro‐scale over sub‐grid modelling in dense gas–solid fluidized flows

Machine Learning Assisted Characterization of Local Bubble Properties and Its Coupling with the EMMS Bubbling Drag

Effect of cathode-side gas flow channels section geometry on the removal process of liquid slug in a proton exchange membrane fuel cell

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