Multi-physics modeling of thermochemical storage in porous medium reactors using the lattice Boltzmann method for heat storage applications: Bridging pore-scale dynamics and macroscopic performance

Abstract

Thermochemical heat storage is of great potential for the development of efficient and sustainable energy systems. This study presents the Representative Elementary Volume (REV) model, applied through the Lattice Boltzmann Method, to simulate the complex thermochemical processes of CaO/Ca(OH)₂ in heat storage applications. The REV model abstracts the intricate fluid transport between pores, using statistical parameters like effective viscosity and porosity to characterize the material properties. In the process of thermochemical reaction, it is not the existence of velocity, temperature and concentration fields alone, but the complex interaction between these fields affecting each other. Different from the typical convective heat transfer simulation, not only heat transfer is considered. The interdependence of these factors needs to be considered. For example, the velocity field has a significant effect on the temperature field and the concentration field, and the similar temperature field will also affect the velocity field and the concentration field. Therefore, we have established a comprehensive numerical model involving multi-physical field coupling of velocity field, temperature field and concentration field to compare and analyze the fluid flow, heat transfer and mass transfer in the reactor at the REV scale. Key findings include the prediction of velocity, concentration, and temperature distributions, with results showing that as porosity decreases, the average flow velocity increase in the flow direction increases. Comparative analysis between REV and pore-scale models reveals consistent trends, validating the REV model accuracy in capturing essential transport phenomena. Results demonstrate that the REV model can accurately predict the macroscopic reactor performance with average discrepancies in temperature and concentration distributions between the scales within 5 %, underscoring the REV model potential for evaluating macroscopic performance while simplifying the computational complexity associated with pore-scale dynamics. This work is significant for enhancing the design and efficiency of thermochemical storage systems, contributing to the broader adoption of renewable energy solutions.