Up-scaling heat transfer in gas-particle mixtures: Eulerian-Lagrangian macro-scale description through volume averaging
Résumé
The risk of dust explosion appears in many industrial situations. In nuclear safety analysis, one of the scenarios is the risk of graphite dust explosion that may occur during decommissioning operations of UNGG reactors [6]. In such a case, the problem is considered as a dispersed two-phase flow with particle size typically ranging from 1 to 100 µm and a particle volume fraction up to 1/1000. The modeling of such reactive dispersed two-phase flows is usually done through a macro-scale Euler-Lagrange approach for which the continuous phase is described in macro-scale Eulerian frame while the dispersed phase is described in a Lagrangian frame by tracking each individual particle into the carrying filtered continuous phase. The modeling of the macro-scale heat exchanges between the filtered continuous phase and particles is usually based on the description of heat transfer from an isolated particle [3, 5]. In this paper, we propose an alternate route to derive the macro-scale Eulerian-Lagrangian description, using the up-scaling methodology based on spatial averaging. The proposed methodology allows us to determine the macro-scale exchange between the continuous phase and the particles directly from the resolution of closure problems on a representative element volume.
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