Experimental and numerical study on exothermic performance of modified expanded graphite and magnesium‑strontium binary chloride composite thermochemical heat storage material

Thermochemical heat storage technologies based on hydrated salt materials play an important role in renewable energy power generation and building heating systems. This study develops a novel MEG-MgCl₂-SrCl₂ composite material, characterizing its excellent sorption and cycle stability. The hydration kinetics, effectively described by a shrinking core model, were experimentally parameterized. Based on the reaction kinetic model and parameters, a multiphysics model of heat transfer, fluid flow and chemical reaction in a closed-type shell-and-tube reactor was established to study the hydration performance of the prepared material and reveal the influence of reactor structure and operating conditions. The results show that the average outlet air temperature of the reactor with baffles increased by 4 °C and the reaction time shortened by 34.0% compared with the reactor without baffles. In addition, when the inlet air velocity increases or the water vapor pressure decreases, the maximum outlet temperature gradually decreases and the effective heating time shortens. When the air inlet speed is 2 m/s and the water vapor pressure is 1350 Pa, the effective heating time is 500 min, which accounts for 71.4% of the total reaction time. In this work, the reaction kinetic parameters of the new composite thermochemical heat storage material were obtained, and the heating effect of the material under typical working conditions was studied through the simulation process, which provided an effective reference for engineering application.