DEM simulation and analysis of particle mixing and heat conduction in a rotating drum

This study investigates mixing and heat conduction of granular particles in a rotating drum by DEM simulation and a particle-particle heat conduction model. Based on the Lagrangian viewpoint, the particle trajectory, velocity, radius of gyration, convolution, temporal intermittency factor, probability density function, and the temperature difference or rate are analyzed to study the characteristics of particle mixing and heat conduction in the drum. The results illustrate a cyclic and intermittently pulsed variation for the radius of gyration and velocity. The intermittency factor and probability density function show the fundamental differences for the cyclic motion characteristics under different rotation velocities. Two mechanisms of mixing augmentation by the increased rotation velocity at the low rotation speed stage and a stable state of a self-maintained equilibrium at the high rotation speed stage are demonstrated, provided the flow regime is not changed. The variations of E(T-h*-T-l*) in time and revolutions show the relative importance of contact duration and mixing on heat conduction, as well as the influencing factor of flow regimes. The increase rates of E(T-h*-T-l*) show the maximum efficiency of particle-particle heat conduction and the most effective operation condition or optimal approach for heat conduction enhancement. (C) 2013 Elsevier Ltd. All rights reserved.