Experimental and numerical analyses of gravity-driven granular flows between vertical parallel plates for solar thermal energy storage and transport

Gravity-driven granular flows between vertical parallel plates were considered at elevated temperatures to examine flow behavior and inform solar thermal energy storage and transport infrastructure design and performance. A series of experiments was performed at inlet temperatures of 23, 200, 400, 600, and 800 degrees C in a high-temperature granular flow experimental rig and spatial and temporal velocity and surface temperature fields were measured. Granular flows were observed to change as a function of temperature. The interaction between the particles and the wall significantly increased with decreases in channel widths. Particle velocities at the outlet of the channel were compared with results from numerical model using the discrete element method. Temperature-dependent flow properties directly related to the assembly were measured and used for granular flow simulation. Flow behavior within the channel was investigated from the simulated results by obtaining particle volume fractions and particle velocities. Wall temperature and outlet granular flow temperature were monitored during the flow experiment and temporal heat loss in the flow was calculated. The granular flow behavior and heat transfer analysis from both the experiment work and simulation provide important mass transfer information for heat transfer modeling at elevated temperature.