Radiative heat transfer with a blocked-off approach for application in the discrete element method

Jaeger, B. and Schlag, M. and Scherer, V. and Wirtz, S. and Schiemann, M.

Volume: 392 Pages: 558-569
DOI: 10.1016/j.powtec.2021.07.010
Published: 2021

Combining the Discrete Ordinates method with the so-called blocked-off approach to calculate radiative heat transfer is investigated for a prospective application in DEM/CFD simulations. Therefore, a single cubic DEM object is located within a prismatic enclosure. The temperature of all walls of the enclosure and of the surface of the DEM object are set to fixed values. The three-dimensional radiative transport is calculated and the heat transfer onto the individual surfaces of the DEM object is determined. A conventional CFD simulation employing a body-conformal mesh at the surface of the embedded DEM object, serves as a reference, an “exact” solution. The results obtained are compared to corresponding solutions with a blocked-off approach, where the shape of the DEM object and the required boundary conditions are enforced within the discretized intensity field while suppressing the solution process in the region obstructed by the object. Mesh-resolution and orientation of the cube in the enclosure are varied and two computationally cheap methods to obtain the radiative fluxes onto the embedded cube surfaces are employed. The heat fluxes onto the cube's surfaces are generally overestimated. This is mainly due to the “artificial” increase of the cube's surface area by the blocked-off approach. The introduction of a simple surface area scaling factor improves the results significantly. The deviation in radiative heat from the exact solution depends on the cube's orientation in the prismatic box and on the position of the actual surface relative to the closest mesh line. The approximation deviates about 1.4% to 3.1% in radiative heat to the cube, values which seem to be acceptable. © 2021 Elsevier B.V.

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