Understanding the varying discharge rates of lognormal particle size distributions from a hopper using the Discrete Element Method

Determination and Validation of Discrete Element Model Parameters of Soybeans with Various Moisture Content for the Discharge Simulation from a Cylindrical Model Silo

This study investigates the physical parameters that affect the flow patterns of soybeans with various moisture content (12% to 60%) at varying orifice sizes (20, 40, and 60 mm) in a cylindrical silo. The flow conditions required to obtain a steady mass flow during discharge were evaluated via experiments and three-dimensional discrete element method (DEM) simulation. The discharged mass flow rates at different flow conditions provided the critical size of the orifice. If the reduced diameter (Dred) of an orifice is >5.59, the flow showed a steady state. Based on the mass flow index (MFI), the flow patterns at 40% and 60% moisture content at 40 and 60 mm orifice sizes, respectively, showed funnel flows. although these flow conditions were satisfied to maintain a steady flow. The maximum wall pressure for the funnel flow showed the location of the interlocking phenomenon where the stagnant zone began during discharging. DEM simulation was validated through the mass profiles using the parameters obtained by the experiments. This study demonstrates that the experimental and analytical results with DEM simulation predict the flow behaviors of soybeans well at various moisture contents. These results are useful for designing silos for continuous food processing.

Modelling of large-particle-motion–heat-transfer coupling characteristics in rotary kiln based on discrete element method

A three-dimensional numerical simulation of the motion – heat-transfer coupling characteristics of waste tyre particles in a rotary kiln at 773–973 K was performed in this study. The particle dynamics and heat transfer characteristics were solved on a Lagrange grid. The motion model considered particle collisions using a nonslip collision model. Based on the particle motion results obtained, we considered three heat transfer mechanisms: particle–particle collision heat conduction, wall–particle radiation heat transfer, and wall–particle collision heat conduction. Subsequently, we established a mathematical model wherein the heat transfer associated with a particle is determined by its position in each time step, and implemented it on a JAVA platform to perform calculations. Finally, we obtained the temperature of each particle at each moment in the entire process. Further analysis of the simulation results shows that the average temperature and temperature standard deviation is governed by the wall temperature, rotation speed, and particle size.