(448af) Intra- and Inter-Particle Resolved Simulations and Experiments on Thermal Transport in Confined Particle Beds

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.