(144b) Thermal Fluxes in Wall Bounded Sheared Granular Beds Near the Jamming Point

Sheared particle beds are encountered in a broad range of engineering applications, such as geophysics or chemical engineering [1]. In order to simulate these particle systems, Discrete Element Method (DEM) and Computational Fluid Dynamics-DEM tools became state of the art over the past ten years [2]. Only recently, DEM-based tools have been extended to account for intra-particle transport processes, opening the door for full-physics simulations of phenomena occurring in applications such as Chemical Looping Combustion or Reforming. For example, our software tool ParScale [3, https://github.com/CFDEMproject/ParScale-PUBLIC] can be linked to the Euler-Lagrange simulation code CFDEM®, is able to resolve intra-particle properties, and accounts for the transmitted heat to the ambient fluid. The scientific exploitation of these new tools is far from being completed, and here we focus on the delicate topic of thermal transport in sheared gas-particle systems.

Until now little effort was made to study the simultaneous impact of the conductive, convective and transmitted flux (to an ambient fluid) inside a sheared particle bed. Often, fully periodic boxes under vacuum conditions in combination with frictionless particles are used [4], which cannot represent a typical application in chemical engineering. This consequently limits the applicability of the conclusions since these model approaches are mostly developed to study the rheological behavior of sheared beds. Also, the thermal transition during jamming of a sheared particle bed is still unknown.

Thus, it is our goal to close this gap in literature by making use of the coupling capability between the DEM code LIGGGHTS® and our library ParScale. We model heat transfer phenomena over a wide range of dimensionless parameters and resolve for intra-particle temperature gradients. Thereby, we focus on flow situations where jamming of the system is reported in literature, discuss arising questions concerning crystallization, and the effect of inter-particle friction. Finally, we present new regime maps for thermal fluxes in sheared particle beds, and discuss novel scaling laws for predicting these fluxes.

REFERENCES

[1] J. R. Rice. Heating and weakening of faults during earthquake slip. Journal of Geophysical Research: Solid Earth, 111(5):1–29, 2006

[2] 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

[3] 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

[4] P. Rognon and I. Einav. Thermal Transients and Convective Particle Motion in Dense Granular Materials. Physical Review Letters, 105:1–4, 2010