A novel method for the calculation of particle heat conduction and resolved 3D wall heat transfer for the CFD/DEM approach

H. Kruggel-Emden, T. Oschmann
Powder Technology
CFD-DEM Simulation, Experiments, Packed Bed, particle-wall contact heat conduction, resolved intra-wall heat conduction, Rotating drum

A novel particle-wall heat transfer coupling algorithm is derived to resolve the heat transfer due to particle-wall contact and inner wall heat conduction. The proposed method is integrated in an existing Computational Fluid Dynamics/Discrete Element Method (CFD/DEM) framework where the particle-wall contact heat conduction is solved through the DEM and set as a source term to the CFD. The 3D temperature profile within the wall is solved in time and space in the CFD. The newly calculated wall temperatures are coupled back to the DEM to elaborate the new particle-wall heat fluxes. Two simulation cases are considered. Firstly, a simple rotating drum is simulated to underline the relevance of the realized wall heat transfer model. The focus is set on the calculation of the temperature evolution of the wall. Therefore, only particle-particle and particle-wall heat transfer mechanisms are considered. We use the material aluminum for both, particles and walls and choose the wall dimensions so that the wall mass is approximately one third of the total particle mass. In addition to that, the particle diameter is set to 8 mm which allows the usage of the lumped capacity approach (spatially constant particle temperature) for solving the particle temperature over time. To validate the particle-wall heat transfer, we compare CFD/DEM simulations involving the materials aluminum and polyoxymethylene (POM) with performed experiments in the second part of our investigation. The following heat transfer mechanisms are accounted for: particle-particle, particle-wall heat conduction, resolved particle and wall inner heat conduction and convection. For the determination of the local heat transfer coefficient of a particle, a distribution function is used. The convective heat transfer between fluid and walls is calculated in the CFD. Particle surface temperatures are compared with measurements of an infrared camera. To show the influence of the particle-wall heat transfer two simulation cases with and without particle-wall heat transfer are performed. The numerical results are in a good agreement with the experiments in case of POM. For the material aluminum where the influence of the particle-wall heat transfer is more pronounced due to a higher thermal conductivity only the model with wall heat transfer fits the experimental results well.

Keywords: CFD/DEM-simulation, experiments, particle-wall contact heat conduction, resolved intra-wall heat conduction, rotating drum, packed bed, 

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