The description of the mixing characteristics is of fundamental interest for modeling mass transport in fixed-bed reactors. A method based on Lagrangian parcel tracking is presented to determine the axial dispersion coefficient in the mechanical dispersion regime from particle-resolved computational fluid dynamics (CFD) results. The impact of fluid dynamic entry effects and the necessary averaging length on the axial dispersion coefficient is studied, showing that the often reported dependency on the entry length is almost not existent, but a result of insufficient averaging, caused by to short bed heights. The axial dispersion coefficients are determined for different particle shapes and a novel reactor wall concept. A strong correlation is found between the relative variance of the axial velocity and the axial dispersion coefficient.

中文翻译：

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细长固定床机械轴向弥散数值研究

混合特性的描述对于模拟固定床反应器中的传质具有重要意义。提出了一种基于拉格朗日包裹跟踪的方法，用于根据粒子分辨计算流体动力学 (CFD) 结果确定机械分散状态中的轴向分散系数。研究了流体动力进入效应和必要的平均长度对轴向弥散系数的影响，表明通常报道的对进入长度的依赖性几乎不存在，而是由于床高过短导致平均不充分的结果。轴向分散系数是针对不同的颗粒形状和新的反应器壁概念确定的。发现轴向速度的相对方差与轴向色散系数之间存在很强的相关性。