Discrete Modeling of Flow and Heat Transfer in High-Temperature Gravity-Driven Granular Flows for Thermal Energy Storage Available to Purchase

Gravity-driven dense granular flow can be a suitable heat transfer fluid (HTF) for high-temperature thermal and thermochemical energy storage (TES and TCES). Compared to analytical and continuum approaches, discrete element method (DEM) based modeling of granular flows can elucidate the particle-scale flow and thermal transport and is thus an attractive alternative approach. The particle-scale mechanical and flow properties such as sliding and rolling friction coefficients and restitution coefficient between particles are key input parameters for DEM simulations and they can vary with temperature. This study develops a DEM model to observe the particle flow and heat transfer characteristics of dense granular flows over a wide range of temperatures (from room temperature up to 800°C). The DEM flow and heat transfer model is validated and then further used to study the effects of particle flow properties on the local particle flow velocity and temperature profiles. Compared to room temperature (23°C) operation, the particle velocity decreases by 57.10% at the particle outlet for the case with an inlet particle temperature T_p,in = 800°C, 31.06% for T_p,in = 600°C, 16.39% for T_p,in = 400°C, and 6.14% for T_p,in = 200°C, showing the significant effect of high temperature operation. The observed inlet and outlet temperature differences are 0.0°C, 3.0°C, 13.9°C, 38.9°C, and 83.4°C for the cases with T_p,in = 23°C, 200°C, 400°C, 600°C, and 800°C, respectively. This work provides particle-scale insights into thermal transport behavior in granular flows, which are useful for designing novel particle-based heat exchangers and solar receivers and reactors.