Abstract Potassium carbonate, K2CO3, has been identified as one of the most promising thermochemical storage materials for the built environment. Where a lot of knowledge has been gained on hydration/dehydration behavior at atmospheric (open system) conditions, little is known of this process under pure water vapor conditions (closed vacuum system). In this paper, for the first time, the equilibrium behavior and reaction kinetics of a K2CO3 composite are investigated under pure water vapor conditions, as present in closed vacuum systems. In this work the metastable behavior of a K2CO3 composite is investigated under vacuum conditions and compared to its metastable behavior under atmospheric conditions. It is found that the metastable zone is also present in vacuum conditions, however induction times in the metastable zone are much shorter which indicates a faster nucleation rate in vacuum conditions. Moreover the effect of inert gasses in a closed system is studied and it is shown that it is critical to remove all sources of non-condensable gasses. Finally in cyclic measurements it is shown that K2CO3 is stable in multi cyclic experiments, concluding that it is a suitable material for a heat battery based on the concept of a closed reactor.

中文翻译：

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封闭式蓄热系统中的 K2CO3

摘要 碳酸钾 K2CO3 已被确定为最有前途的建筑环境热化学储存材料之一。虽然在大气（开放系统）条件下已经获得了大量关于水合/脱水行为的知识，但对纯水蒸气条件（封闭真空系统）下的这一过程知之甚少。在本文中，首次在封闭真空系统中的纯水蒸气条件下研究了 K2CO3 复合材料的平衡行为和反应动力学。在这项工作中，研究了 K2CO3 复合材料在真空条件下的亚稳态行为，并与其在大气条件下的亚稳态行为进行了比较。发现在真空条件下也存在亚稳区，然而，亚稳区的诱导时间要短得多，这表明真空条件下的成核速度更快。此外，还研究了封闭系统中惰性气体的影响，结果表明去除所有不可冷凝气体来源至关重要。最后在循环测量中表明，K2CO3 在多循环实验中是稳定的，基于封闭反应堆的概念得出结论认为它是一种适合热电池的材料。