Granular flow characteristics and heat generation mechanisms in an agitating drum with sphere particles: Numerical modeling and experiments

This work focuses on mechanism of heat generation in an agitating drum with dense gas-solid flow where particles move at high velocity (30 m/s). Numerical simulations and experiments are used to study the influence of granular flow characteristics, design parameters, process parameters and particle properties in heat generation and energy-conversion coefficient. Heat generates from sliding friction, rolling friction, viscous force of liquid-bridge or the modeled particle deformation. The variable goes to liquid volume due to high temperature (533 K) in wet particle flows. Concerning the velocity and particle motion several thermal transfer models are modified to match particle/particle and particle-wall/blade collisions, which are integrated to DEM-CFD numerical simulation. Experiments detected the temperature of external drum wall, the effect of temperature on liquid phase and the granular motion by visualization tests. The numerical results are verified by experimental data with good agreements. The effects of agitating speed and initial filling degree on temperature increase are not always in positive correlation, which are more significant in wet particles flow. Numerical simulations predicted the dynamic particles characteristic, the heat resources and the thermal conduction to reveal the heat generating mechanisms. Besides, the improved blades design to enhance heat generation is analyzed qualitatively and deduced.