468350 Intra- and Inter-Particle Resolved Simulations and Experiments on Thermal Transport in Confined Particle Beds

Tuesday, November 15, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Thomas Forgber, Federico Municchi, Thomas Puffitsch and Stefan Radl, Institute of Process and Particle Engineering, Graz University of Technology, Graz, Austria

Currently, numerical studies on thermal transport in dense gas-particle suspension flows often rely on a number of simplifications, e.g., (i) a uniform intra-particle temperature profile [1], or (ii) a two dimensional formulation [2]. This clearly limits the applicability of these previous studies, often leaving open questions related to the relative importance of intra-particular transport phenomena. It is the goal of our present work to close this gap by establishing an open-source simulation environment, and demonstrate the validity of the employed models and tools within an array of canonical flow situations.

In the present contribution we experimentally and numerically investigate the energy transport in dense particle beds that are confined by two walls. Therefore, we use the well-established Eulerian-Lagrangian simulator CFDEM® [3]. Also, we make use of the novel coupling capabilities of this simulator with the recently developed intra-particle solver ParScale [4]. Our numerical studies focus on two methods: first, we simulate the details of flow and temperature fields in the fluid phase by means of Direct Numerical Simulation (DNS). Therefore, we use a novel Hybrid Fictitious-Domain/Immersed-Boundary (HFDIBM) approach to accurately impose the Dirichlet boundary condition at the particle surfaces. Coupling of the HFDIBM with ParScale enables us (i) to make direct predictions of intra- and inter-particle heat fluxes, as well as (ii) to derive particle-based Nusselt numbers. The latter are compared to correlations available from literature in order to identify opportunities for the improvement of these correlations. Second, we perform unresolved CFD-DEM-based simulations, which benefit from the understanding gained from our DNS in terms of closures for the heat transfer rate. By coupling the CFD-DEM simulations with ParScale, we are now in the position to evaluate the effect of intra-particular heat fluxes on the overall transferred amount of heat with relative ease (see Figure). Finally, we compare our results with experiments of fixed and fluidized beds, as well as simple 1D models.

Figure: Temporal progression of the mean particle temperature vs. bed height in a fluidized bed based on CFD-DEM simulations with ParScale (solid lines), and without intra-particle heat transfer (dashed lines; in both simulations the Biot number is ca. 0.8).

References

[1]   Z. Feng, S. Musong. Direct numerical simulation of heat and mass transfer of spheres in a fluidized bed. Powder Technology, Vol. 262, pp. 62-70, 2014.

[2]  R. Schmidt, P. Nikrityuk. Numerical simulation of the transient temperature distribution inside moving particles, The Canadian Journal of Chemical Engineering, Vol.  90, pp. 246-262, 2012.

[3]   C. Kloss, C. Goniva, A. Hager, S. Amberger, S. Pirker (2012) “Models, algorithms and validation for opensource DEM and CFD-DEM”, Progress in Computational Fluid Dynamics, Vol. 12, Nos. 2/3, pp.140–152, 2012.

[4]  S. Radl, T. Forgber, A. Aigner, C. Kloss, ParScale - An Open-Source Library for the  Simulation of Intra-Particle Heat and Mass Transport Processes in Coupled Simulations, in: E. Onate, M. Bischoff, D.R.J. Owen, P. Wriggers, T. Zhodi (Eds.), IV Int. Conf. Part. Methods – Fundam. Appl. (PARTICLES 2015), ECCOMAS, Barcelona, Spain, 2015: pp. 1–9.

 


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