On the application of an Eulerian granular model towards dilute phase pneumatic conveying

Abstract

The present study considered the application of a multiphase model with Eulerian approach for the solids phase in dilute-phase conveying, where the results are compared against previously published experimental results based on 42µm nominal diameter glass particles. In particular, the Favre-Averaged Drag turbulent dispersion model is studied where it is found to have greater effects on the particle concentration distribution as compared to the gas phase velocity. While certain discrepancies are observed between simulations and published experimental data, the flow characteristics are adequately captured after addressing the underlying cause of inaccuracies. Inaccuracies in the particle concentration distributions along a vertical pipe section result from the difficulty in capturing the transitional zone where the particle rope starts to disperse. On the other hand, particle diameter variations underpin the mismatches along a horizontal pipe section. Interestingly, increasing particle diameter leads to the successful capturing of the particle concentration distribution along the horizontal pipe section. The accuracy of employing an Eulerian approach for solids phase is demonstrated, provided that the particle diameter is accounted for.

Application of an Eulerian granular numerical model to an industrial scale pneumatic conveying pipeline

“…The radial distribution function g 0,ss is: (12) where α s,max is the packing limit of the solids phase. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 31 The turbulent dispersion force in equation 5 is: (13) where is a modifiable constant, is the interphase momentum exchange coefficient, is the turbulent Prandtl number and the dispersion scalar is estimated by: (14) The momentum exchange between phases or, interphase momentum exchange term, obeys the following constrain that: (15) and is modelled using the differences in velocities between the two phases: (16) where is an interphase momentum exchange coefficient.…”

“…At the walls, different treatments are applied for both of the phases. A no-slip condition is applied for the gas phase and a specularity coefficient of 0.6 is applied for the solid phase, similar to an earlier study by the authors [12] where it produced good agreements with real-world observations. The specularity coefficient is used for a rough wall and it defines the collision characteristics of a particle with the wall, with a value of 0 being a perfectly smooth wall.…”

“…Following previous work [12], where the Eulerian granular model had been shown to capture cement flows reasonably well, this study will adopt the same model with changes to the solid phase material properties to fit the current cement conveying investigation. The Eulerian granular model has been adopted using Fluent (ANSYS Inc.).…”

“…Wall lubrication force is only pertinent to bubbly multiphase flows and virtual mass force is appropriate only when the density of the secondary phase is much lesser than that of the primary phase. This leaves the reduced solid [12]. The authors of the FAD model stopped short of providing guidelines on their model's applicability to which it could not be immediately determined if the FAD model is suited for the current study.…”

“…In this study the cells are now sized at about 0.004 × 0.004 × 0.008m. Earlier, a mesh dependency test [12] was conducted on three different sized meshes with the same numerical model. It was found that two of the finer meshes did not 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 10 differ while the coarser mesh only differs a little from the other two.…”