In this study, a numerical analysis is used to compare the effects of uniform and cascaded graphite foams on the charge–discharge cycle performance of thermal energy storage systems where a phase change material (PCM) with a phase change temperature of 855 K is used as the storage media. Firstly, for a constant PCM mass, the insertion of single graphite foams with respective porosities of 80%, 85%, 90% & 95% in the storage tank resulted to an exponential increase in the charge–discharge time. It was therefore concluded that a graphite foam with a porosity higher than 90% is less beneficial because the gradient of the porosity versus charge–discharge time graph becomes steeper. Secondly, for a constant PCM mass, graphite foams of porosity 80%, 85% and 90% were combined to obtain a cascaded porosity structure. The three foam structures were cascaded in such a way that the average porosity was either 85% or 89%. Overall, results obtained for cascaded porosity structures showed that combinations having a low porosity graphite foam near the cooling/heating wall performed better than their counterparts having a higher porosity foam near the heating/cooling wall. Particularly, the best combination at an average porosity of 85% and 89% accelerated the charge–discharge time by 5% and 4%, respectively, as compared to their respective single graphite foam cases.

在这项研究中，使用数值分析来比较均匀和级联的石墨泡沫对热能存储系统的充放电循环性能的影响，在该系统中，相变温度为855 K的相变材料存储介质。首先，对于恒定的PCM质量，在储罐中插入孔隙率分别为80％，85％，90％和95％的单个石墨泡沫会导致充放电时间呈指数增长。因此可以得出结论，孔隙率高于90％的石墨泡沫的益处较小，因为孔隙率与充放电时间图的梯度变大了。其次，对于恒定的PCM质量，将孔隙率分别为80％，85％和90％的石墨泡沫混合，以获得级联的孔隙结构。三种泡沫结构以平均孔隙率为85％或89％的方式级联。总体而言，级联孔隙结构的结果表明，在冷却/加热壁附近具有低孔隙度石墨泡沫的组合比在加热/冷却壁附近具有较高孔隙度泡沫的同行表现更好。特别是，平均孔隙率分别为85％和89％的最佳组合相比，它们各自的单个石墨泡沫塑料外壳的充放电时间分别缩短了5％和4％。级联孔隙结构获得的结果表明，在冷却/加热壁附近具有低孔隙度石墨泡沫的组合比在加热/冷却壁附近具有较高孔隙度泡沫的同行表现更好。特别是，平均孔隙率分别为85％和89％的最佳组合相比，它们各自的单个石墨泡沫外壳分别将充放电时间缩短了5％和4％。级联孔隙结构获得的结果表明，在冷却/加热壁附近具有低孔隙度石墨泡沫的组合比在加热/冷却壁附近具有较高孔隙度泡沫的同行表现更好。特别是，平均孔隙率分别为85％和89％的最佳组合相比，它们各自的单个石墨泡沫外壳分别将充放电时间缩短了5％和4％。