Tomography-based pore-scale model and prediction of flow and thermal transport properties for thermochemical energy storage materials

Thermochemical energy storage (TCES) has attracted significant attention in the energy storage community due to its high energy density and intrinsic cyclability. In this research, the influence of pore-scale structural changes through reduction-oxidation cycles on the effective flow and thermal transport properties of magnesium-manganese-oxide (Mg-Mn-O, a viable TCES material) are studied. Representative pore geometries of Mg-Mn-O cylindrical and spherical pellets are obtained through X-ray computed tomography and subsequent 3D reconstruction. Numerical simulations of the fluid flow and heat transfer in the reconstructed porous media are performed with the lattice Boltzmann method (LBM). A wide array of fluid velocities is studied to demonstrate the Darcian and non-Darcian flow regimes. The effective thermal conductivity of the porous matrix is determined for Mg-Mn-O and air mixtures over a wide temperature range, and the results are compared to classic correlations available in the literature. Flow and heat transfer correlations for the studied samples are derived and presented herein. This work provides a promising approach to predict pore-scale flow and heat transfer in re-constructed porous media with real geometrical effects, which can be extended to include reactive species transport and evolving pore-structures to better understand the pore-evolution and reaction mechanisms.