(224e) A Novel Approach for Radiative Thermal Exchange in Coupled Particle Simulations

Radiative thermal heat exchange in particulate systems is of major importance in a variety of industrial applications, ranging from chemical reactors, thermal insulation, powder metallurgy, solar-thermal receivers, laser sintering, combustion processes and many other domains. Various experimental studies (see e.g. Chen et al. [1], Goshayeshi et al. [2]) show, that thermal transport through radiation becomes the leading heat transfer mechanism at high temperatures, i.e., above 750°C. In the contrary, numerical studies on thermal transport in dense gas-particle suspension flows are often limited to conductive and convective thermal transport (Forgber and Radl [3]).

The goal of our present work is to introduce a novel approach to predict radiative energy exchange rates in Discrete Element Method (DEM) simulations. Previously, computationally expensive approaches, e.g. Monte Carlo or inline ray-tracing (Dayal [4]), were used to study this mode of energy exchange. Unfortunately, such approaches limit the application to small particle arrangements. We introduce a novel, efficient method for thermal exchange through radiation and extend the capabilities of the open-source particle simulator LIGGGHTS (Kloss et al. [5]). The method is based on a per-particle view factor evaluation which utilizes standard discrete element method routines (see Forgber and Radl [6]). Subsequently, the energy transport in dense sheared particle beds is investigated numerically, and the relative importance of radiation compared to other heat transfer mechanisms is quantified. Most important, our present contribution further explores the influence of boundaries. Therefore, we (i) present a simplified setup which includes heated walls, (ii) detail on the numerical model, and (iii) discuss the formulation of the boundary conditions that needs to be used. Our results are helpful to decide whether radiative wall-particle heat transfer must be considered in a numerical model or not.

References

[1] J. C. Chen, J. R. Grace, and M. R. Golriz. Heat transfer in fluidized beds: design methods. Powder Technology, 150(2):123–132, 2005.

[2] A. Goshayeshi, J. R. Welty, R. L. Adams, and N. Alavizadeh. Local Heat Transfer Coefficients for Horizontal Tube Arrays in High-Temperature Large-Particle Fluidized Beds: An Experimental Study. Journal of Heat Transfer, 108(4):907–912, 1986.

[3] T. Forgber and S. Radl. Heat transfer rates in wall bounded shear flows near the jamming point accompanied by fluid-particle heat exchange. Powder Technology, 315:82-193, 2017.

[4] R. Dayal. Numerical Modelling of Processes Governing Selective Laser Sintering. PhD thesis, Technische Universität Darmstadt, 2014.

[5] C. Kloss, C. Goniva, A. Hager, S. Amberger, and S. Pirker. Models , algorithms and validation for opensource DEM and CFD-DEM. Progress in Computational Fluid Dynamics, 12:140–152, 2012.

[6] T. Forgber and S. Radl. A novel approach to calculate radiative thermal exchange in coupled particle simulations. Powder Technology, 323:24-44, 2018.