基于 MgSO₄的热化学储能特性数值研究

A charging/discharging model of a two-dimensional porous medium MgSO₄·7H₂O/ MgSO₄ was developed using reaction kinetics to investigate the energy storage characteristics of MgSO₄ as a thermochemical material. This study examined the reaction rate, temperature distribution, and water vapor concentration distribution during heat and mass transfer in charging/discharging units. This study also examined the influence of inlet air temperature (T_in) and inlet air velocity (U_in) on unit performance and thermal efficiency. The results indicate that during the charging process, heat storage increases by approximately 3.13% for every 10 ℃ increase in T_in and by approximately 0.97% for every 0.125 m/s increase in U_in. An increase in T_in accelerates the rate of unit heat transfer and enables the water vapor pressure to reach equilibrium faster, subsequently increasing the reaction rate. Similarly, an increase in U_in enhances the water vapor transport rate and improves the convective heat transfer within the unit, thereby enhancing the kinetic properties and increasing the reaction rate, which leads to an increase in the heat storage capacity. Conversely, during the discharge process, the unit thermal efficiency exhibited an inverse relationship with heat storage capacity. The thermal efficiency decreased by approximately 0.93% for every 2.5 ℃ increase in T_in, whereas heat storage decreased by approximately 0.58% for every 0.1 m/s increase in U_in. An increase in T_in increases the equilibrium pressure of the unit and decreases its unit reaction rate, thereby reducing the effect of temperature rise of the unit. Furthermore, an increase in U_in increases the rate of water vapor transport and convective heat transfer of the unit, which subsequently increases the water vapor pressure. Ultimately, the reaction rate and thermal efficiency decreased.