In recent years, one of the most important issues is optimization of thermal energy-storing technologies. Using phase change materials (PCMs) with specific phase change temperatures allows us to store latent heat as thermal energy. This is one of the most efficient ways to store thermal energy. The objective of this paper is to investigate the discharge performance of a packed bed filled with multi layers of high temperature encapsulated PCMs through a CFD modeling via Comsol multi-physics software. Results of simulation are compared to results of the experimental researches of the literature and there is good agreement between them. The influence of each layer's height and porosity along with different configurations of the PCMs according to their phase change temperatures (ascending and descending in flow direction) are analyzed. It is observed that increasing the inlet velocity of heat transfer fluid (HTF) and increasing the porosity of layers of PCM in the packed bed have similar outcomes and makes the packed bed deplete more rapidly. Some new configurations are suggested and optimized regarding Δ t, which is defined as the ratio between duration of receiving energy with desired temperature to total discharge time of the packed bed, during the discharge process. Results indicate that by setting the layer heights of the PCMs in a descending order and also having the porosity of each layer to decrease in the flow direction, results with 29.2% better performance can be obtained. Optimization of Δt can be a defining factor in designing of packed beds and also a concentrating solar power (CSP) plant.

中文翻译：

---

具有不同层结构的高温相变材料 (PCM) 填充床的 CFD 建模和研究

近年来，最重要的问题之一是热能存储技术的优化。使用具有特定相变温度的相变材料（PCM）使我们能够将潜热存储为热能。这是储存热能最有效的方法之一。本文的目的是通过 Comsol 多物理场软件进行 CFD 建模，研究填充多层高温封装 PCM 的填充床的放电性能。将仿真结果与文献的实验研究结果进行比较，两者吻合较好。分析了各层高度和孔隙率以及相变材料的不同构型对相变温度（沿流动方向上升和下降）的影响。据观察，增加传热流体 (HTF) 的入口速度和增加填充床中 PCM 层的孔隙率具有类似的结果，并使填充床消耗得更快。针对Δt，提出并优化了一些新的配置，Δt定义为在放电过程中接收具有所需温度的能量的持续时间与填充床的总放电时间之间的比率。结果表明，通过按降序设置相变材料的层高，并且使每层的孔隙率沿流动方向减小，可以获得性能提高29.2%的结果。Δt 的优化可能是填充床和聚光太阳能 (CSP) 发电厂设计的决定性因素。