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首页> 外文期刊>International Journal of Heat and Mass Transfer >Direct numerical simulation study of end effects and D/d ratio on mass transfer in packed beds
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Direct numerical simulation study of end effects and D/d ratio on mass transfer in packed beds

机译：填充床传质中末端效应和D / d比对传质的直接数值模拟研究

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Direct Numerical Simulation (DNS) was performed to investigate the end effects on mass transfer in a packed bed for Reynolds number (Re) ≤ 100. The system considered in this study was naphthalene-air with a Schmidt number (Sc) ∼ 2.52. The location of the spheres’ centers in a randomly packed bed were obtained from Discrete Element Method – Computational Fluid Dynamics (DEM-CFD) simulations. The influence of the confining wall on how packed bed ends affect mass transfer was studied by examining the axial void fraction profile with varying ratio of the column diameter to the particle sphere diameter (D/d). Overall, it was found that the confining wall has a significant impact. The ‘local’ mass transfer coefficient was calculated based on the obtained DNS results and the probability distribution curve and the spatial distribution of the computed ‘local’ Sherwood numbers as function of the ratio X/L (ratio of the height of the active part of the bed to the total height of the bed) were developed to quantify the end effects on mass transfer within packed beds. For a packed bed with no wall effects (D/d = 11), it was found that the end effects can be eliminated by replacing the active particles located at ∼2 sphere diameters from the entrance and ∼1 sphere diameter from the exit by inert particles.
机译：进行了直接数值模拟（DNS），以研究雷诺数（Re）≤100的填充床中传质的最终影响。本研究中考虑的系统是施密特数（Sc）〜2.52的萘-空气。通过离散元方法-计算流体动力学（DEM-CFD）模拟获得了球在随机填充床上的中心位置。通过检查轴向空隙率分布图（柱直径与颗粒球直径的比率（D / d）不同），研究了围壁对填充床末端如何影响传质的影响。总的来说，发现围墙具有重大影响。根据获得的DNS结果，概率分布曲线和所计算的“本地”舍伍德数的空间分布，以X / L比（函数的有效部分的高度比）为函数，计算出“局部”传质系数。床到床的总高度）被开发出来，以量化填充床内传质的最终影响。对于没有壁效应的填充床（D / d = 11），发现可以通过用惰性气体代替入口处约2个球体直径和出口处约1个球体直径的活性颗粒来消除最终效应。粒子。

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