PDF(Pubmed)
Abstract：
This research focuses on modeling heat transfer in heterogeneous media composed of stacked spheres of paraffin as a perspective polymeric phase-change material. The main goal is to study the requirements of the numerical scheme to correctly predict the thermal conductivity in a periodic system composed of an indefinitely repeated configuration of spherical particles subjected to a temperature gradient. Based on OpenFOAM, a simulation platform is created with which the resolution requirements for accurate heat transfer predictions were inferred systematically. The approach is illustrated for unit cells containing either a single sphere or a configuration of two spheres. Asymptotic convergence rates confirming the second-order accuracy of the method are established in case the grid is fine enough to have eight or more grid cells covering the distance of the diameter of a sphere. Configurations with two spheres can be created in which small gaps remain between these spheres. It was found that even the under-resolution of these small gaps does not yield inaccurate numerical solutions for the temperature field in the domain, as long as one adheres to using eight or more grid cells per sphere diameter. Overlapping and (barely) touching spheres in a configuration can be simulated with high fidelity and realistic computing costs. This study further extends to examine the effective thermal conductivity of the unit cell, particularly focusing on the volume fraction of paraffin in cases with unit cells containing a single sphere. Finally, we explore the dependence of the effective thermal conductivity for unit cells containing two spheres at different distances between them.
摘要：
这项研究的重点是模拟由石蜡堆叠球作为透视聚合物相变材料组成的异质介质中的传热。主要目标是研究数值方案的要求，以正确预测由受到温度梯度的球形颗粒的无限重复配置组成的周期性系统中的热导率。基于OpenFOAM,创建了一个模拟平台，通过该平台系统地推断了精确传热预测的分辨率要求。该方法针对包含单个球体或两个球体的配置的单位单元进行了说明。在网格足够精细以具有覆盖球体直径距离的八个或更多个网格单元的情况下，可以建立证实该方法二阶精度的渐近收敛率。可以创建具有两个球体的配置,其中在这些球体之间保留小间隙。发现即使这些小间隙的分辨率不足，也不会为域中的温度场产生不准确的数值解，只要每个球体直径坚持使用八个或更多的网格单元。可以以高保真度和实际计算成本来模拟配置中的重叠和(几乎)接触球体。这项研究进一步扩展到检查晶胞的有效热导率，在单位细胞包含单个球体的情况下，特别关注石蜡的体积分数。最后,我们探索了包含两个球体之间不同距离的晶胞的有效热导率的依赖性。
