Exploring irradiated granular flows with rapid heating for concentrated solar thermal energy collection and storage

Gravity-driven granular flows along an inclined plane were considered with exposure to different levels of irradiation. Experiments were performed with average normal radiative heat fluxes of 400, 500, and 600 kW/m², and the spatial and temporal free-surface velocity and temperature fields were measured. Granular flow behavior changed under different irradiation, primarily due to an increase in particle friction changing with increased temperatures. A transient, pseudo-two-dimensional heat and mass transfer model was developed to capture the relevant heat transfer mechanisms in these flows. The model considered irradiation penetration, effective conduction heat transfer, and non-uniform velocity profiles. The predicted steady state free-surface temperatures were well-correlated to experimental measurements with Pearson's correlation coefficients >0.9. The model predicted a large temperature gradient in the flow due to irradiation attenuation, flow velocity variations in depth, and low effective thermal conductivity. This study effectively captured the heat transport of the irradiated inclined plane granular flows.