Abstract: Heat storage systems are used to reduce the mismatch between heat supply and heat demand. Compared to sensible and latent heat storage,thermochemical heat storage has two major advantages:high heat storage density and long-period storage capability at ambient temperature without extra thermal insulation.In this study,the thermal behavior of Mg/MgH₂ thermochemical heat storage system is numerically investigated.A mathematical model for considering the exothermic process of heat storage is developed,and the influence of different boundary conditions is examined.The results indicate that heat transfer plays a key role in overall thermochemical heat storage efficiency,and an optimum reaction temperature exists which leads to a maximum discharging power for a given heat transfer coefficient.When the boundary condition is constant wall temperature,the system has a maximum discharging power 0.79 kW?(kg Mg)^-1.

Key words: thermochemical heat storage, magnesium hydride, numerical computation, heat release

摘要： 蓄热系统是解决热量供需不匹配的有效方式之一。根据热量储存原理的不同,可以将系统分为显热、潜热和热化学蓄热三种类型,其中热化学蓄热有其独特的优点。基于镁-氢化镁热化学蓄热系统蓄放热时的物理化学过程,建立了系统的二维非稳态数学模型,考虑了不同边界条件对系统的影响,通过数值计算,获得了系统的温度、反应速率、反应进度分布及系统的对外放热功率。研究结果表明:系统的蓄热密度为0.85 kW·h·(kg Mg)^-1,热量的传递是影响系统蓄放热效率的关键因素之一,并且当边界对流传热系数保持一定时,存在一个最佳的外界流体温度,使系统的平均放热功率达到最大。在系统以定壁温为边界条件时,系统最大的平均放热功率/质量值为0.79 kW·(kg Mg)^-1。

关键词: 热化学蓄热, 氢化镁, 数值计算, 放热