A DNS study of flow and heat transfer through slender fixed-bed reactors randomly packed with spherical particles

Abstract

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Multiscale modeling of fixed-bed reactors with porous (open-cell foam) non-spherical particles: Hydrodynamics

“…It is important to mention here that the no-slip boundary condition at the cylindrical wall in a Cartesian domain is enforced by the immersed boundary method, detailed in our previous work [19].…”

“…The computational cells near the particle surfaces are partially occupied by the porous particles. In the present study, the porosity ( D 3 polyhedral volumes formed by grid lines and particles) of such cells is calculated numerically, by dividing the computational cells into very small sub-cells [19]. By counting the number of sub-cells that are inside the particle, the particle volume in that cell and then porosity of that cell is calculated (detailed description in Das et al [19]).…”

“…In the present study, the porosity ( D 3 polyhedral volumes formed by grid lines and particles) of such cells is calculated numerically, by dividing the computational cells into very small sub-cells [19]. By counting the number of sub-cells that are inside the particle, the particle volume in that cell and then porosity of that cell is calculated (detailed description in Das et al [19]). In all calculations presented in this work, we divide each cell into × × 10 10 10 sub-cells, which provides us with an accuracy of ∼ 0.1% with respect to the porosity calculation.…”

“…The drag closure (flow resistance) for the fluid-foam interaction at the micro-scale has been obtained separately by performing fully resolved direct numerical simulations using idealized geometry of a single unit-cell of open-cell solid foams [18]. The cylindrical wall effect is important for slender packed beds and in the adopted Cartesian computational domain it is resolved by an implicit, sharp interface immersed boundary method (IBM) [19]. A challenging task is to computationally generate random packings of non-spherical particles (rectangular or cubic shaped particles).…”

Effect of Gas Velocity Distribution on Heat Recovery Process in Packed Bed of Plate-Shaped Slag

“…In case of a small tube-to-particle diameter ratio, the wall effect is clearly observed as an increase of the void fraction. Das et al [15] also thoroughly evaluated the wall effect of a packed bed of spherical particles in slender columns. The radial porosity distributions in many cases with different tube-to-particle diameter ratios were introduced in their work, along with the effect of the Because of the lower heat conductivity of the slag compared to other packed materials such as coke, shape control of the slag during solidification is important for obtaining high temperature gas from the hot slag.…”