Thermochemical heat storage (TCHS) technology plays a crucial role in the energy system, essential for maintaining the balance between energy supply and demand. The Ca(OH)/CaO system holds significant promise for TCHS thanks to its high energy storage density, cost-effectiveness, and minimal heat loss. However, further research is required to elucidate the coupling mechanisms of the various physicochemical processes involved and to optimize the overall system performance. This paper focuses on assessing and elucidating the multi-physics coupled transport rules during both the charging and discharging stages in a fixed-bed reactor based on the developed numerical model. Results manifest the bed temperature rapidly increases to around 950 K, then slows down as the endothermic reaction predominates, completing dehydration in 1,900 s. During discharging, hydration conversion advances in a “U”-shaped pattern from the vapor inlet and side wall to the outlet, driven by the high vapor content near the inlet and the lower temperature near the wall. Furthermore, a thorough sensitivity analysis of the main parameters such as thermal conductivity and porosity is conducted to determine how different operating conditions affect the charging and discharging processes. Finally, a new reactor structure is proposed, in which a gas-guide duct is added at the central axis of the reactor to improve mass transport and uniformly distributed finned heating tube bundles to enhance heat transfer. These two functions can shorten the charging period by 9 % and 16 % respectively. The results can aid in predicting thermochemical conversion behaviors and multi-physic coupling transport processes, while also providing a foundational reference for the design of TCHS systems.

中文翻译：

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Ca(OH)2/CaO在固定床反应器中热化学充放热行为研究


热化学储热（TCHS）技术在能源系统中发挥着至关重要的作用，对于维持能源供需平衡至关重要。 Ca(OH)/CaO 系统因其高能量存储密度、成本效益和最小的热损失而对 TCHS 具有重大前景。然而，需要进一步的研究来阐明所涉及的各种物理化学过程的耦合机制并优化整体系统性能。本文重点基于所开发的数值模型评估和阐明固定床反应器充电和放电阶段的多物理耦合输运规则。结果表明，床温迅速升高至 950 K 左右，然后随着吸热反应占主导地位而减慢，在 1,900 秒内完成脱水。在放电过程中，水化转化以“U”形模式从蒸汽入口和侧壁到出口进行，这是由入口附近的高蒸汽含量和壁附近的较低温度驱动的。此外，对热导率和孔隙率等主要参数进行了彻底的敏感性分析，以确定不同的操作条件如何影响充电和放电过程。最后，提出了一种新的反应器结构，其中在反应器的中心轴处增加气体导管以改善传质，并在反应器的中心轴处增加均匀分布的翅片加热管束以增强传热。这两项功能可分别缩短充电时间9%和16%。研究结果有助于预测热化学转化行为和多物理耦合输运过程，同时也为 TCHS 系统的设计提供基础参考。