Abstract Owing to its high heat storage capacity and fast heat transfer rate, packed bed latent heat storage (LHS) is considered as a promising method to store thermal energy. In a packed bed, the wall effect can impact the packing arrangement of phase change material (PCM) capsules, inducing radial porosity oscillation. In this study, an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation. Its fluid flow and heat transfer were analyzed. With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed, the corresponding relationships between the arrangement of capsules and porosity oscillation were identified. The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid (HTF) velocity. As a result, radial temperature distributions and liquid fraction distributions of PCMs were further affected. The effects of different dimensionless parameters (e.g., tube-to-capsule diameter ratio, Reynolds number, and Stefan number) on the radial characteristics of HTF and PCMs were discussed. The results showed that different diameter ratios correspond to different radial porosity distributions. Further, with an increase in diameter ratio, HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease. The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF—while higher Reynolds numbers can lead to a proportional improvement of velocity, an increase in Stefan number can promote heat storage of the packed bed LHS system.

中文翻译：

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径向孔隙度振荡对填充床潜热蓄热热性能的影响

摘要 填充床潜热蓄热（LHS）由于其储热能力高、传热速度快，被认为是一种很有前景的热能储存方法。在填充床中，壁效应会影响相变材料 (PCM) 胶囊的填充排列，从而引起径向孔隙度振荡。在这项研究中，建立了一个基于实际布置的三维填充床 LHS 模型来考虑径向孔隙度振荡。对其流体流动和传热进行了分析。在填充床中沿径向截取不同的圆柱形子表面，确定了胶囊排列与孔隙度振荡之间的对应关系。径向孔隙度的振荡分布导致传热流体 (HTF) 速度的非均匀分布。因此，PCM 的径向温度分布和液体分数分布进一步受到影响。讨论了不同的无量纲参数（例如，管与胶囊的直径比、雷诺数和斯蒂芬数）对 HTF 和 PCM 的径向特性的影响。结果表明，不同的直径比对应不同的径向孔隙度分布。此外，随着直径比的增加，近壁区域的HTF速度变化显着，而中心区域的HTF速度的不均匀性将降低。Reynolds 和 Stefan 数略微影响 HTF 的相对速度分布——而较高的 Reynolds 数可以导致速度成比例的提高，Stefan 数的增加可以促进填充床 LHS 系统的热量储存。