The transient heat transfer behaviours in a packed bed have been studied using coupled computational fluid dynamics (CFD) and discrete element method (DEM). Intra-particle thermal diffusion, which is a crucial but rarely explored issue, is considered by introducing a one-dimensional diffusion equation in the DEM solver. To achieve a sufficiently long physical time of simulations, we further reduce the computational cost by applying periodic boundary condition to a small segment of the packed bed. Our study demonstrates a shifting peak heat flow rate from the bottom to the top of the packed bed during the initial warming phase. We affirm that the influence of thermal diffusion within a particle is noteworthy only for particles exhibiting a high Biot number (e.g., Bi = 1.2). This insight enriches our understanding of heat transfer mechanisms in packed beds and their practical engineering applications.

中文翻译：

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填充床中瞬态气固传热的数值研究：颗粒内热扩散的影响

使用耦合计算流体动力学 (CFD) 和离散元方法 (DEM) 研究了填充床中的瞬态传热行为。颗粒内热扩散是一个至关重要但很少被研究的问题，通过在 DEM 求解器中引入一维扩散方程来考虑。为了实现足够长的物理模拟时间，我们通过将周期性边界条件应用于填充床的一小部分来进一步降低计算成本。我们的研究表明，在初始升温阶段，峰值热流量从填充床的底部转移到顶部。我们确认，颗粒内热扩散的影响仅对于表现出高毕奥数（例如 Bi = 1.2）的颗粒才值得注意。这一见解丰富了我们对填充床传热机制及其实际工程应用的理解。