Discrete Element Modeling of a Particle Heater for Energy Storage Systems

A heater where particles fall under gravity and flow over a series of hot angled surfaces is simulated. The conductive, convective, and interphase heat transfer are simulated for all particles via discrete element modeling (DEM). The heater inclination angle, particle-particle and particle-wall friction coefficients, and thermal contact resistances are parametrically varied. Decreasing the inclination angle increases the residence time and overall heat transfer coefficient. Low values of the friction coefficients slow the particles and increase heating, but moderate to high values of friction dilute the flow and decrease the heat transfer. The contact resistance between particles is difficult to accurately characterize, so a wide range is studied. The contact resistance is altered by varying the particle roughness from 27.5 nm to 1 μm, which reduces the overall heat transfer coefficient by 25%. A reduced order model is developed and validated to extrapolate the small-scale DEM results to a larger-scale system.