A DNS study of flow and heat transfer through slender fixed-bed reactors randomly packed with spherical particles
A DNS study of flow and heat transfer through slender fixed-bed reactors randomly packed with spherical particles
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DOI：
10.1016/j.ces.2016.11.008
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发表时间：
2017-03
影响因子：
4.7
通讯作者：
Saurish Das;N. Deen;J. Kuipers
中科院分区：
文献类型：
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作者：
Saurish Das;N. Deen;J. Kuipers
本文提出了一种细长随机填充床反应器流动与传热的全分辨直接数值模拟方法。流场和温度场的求解在一个非贴体，非保形笛卡尔计算域。流体和固体（球形颗粒和圆柱壁）之间的耦合是由二阶精度，尖锐的界面浸入边界方法（IBM）。目前的数值技术既不需要任何具有挑战性的体积网格生成过程，也不需要操纵的几何形状附近的颗粒颗粒和颗粒壁接触点。共轭传热已被认为是在固体颗粒和流体中的温度场计算。采用离散元法（DEM）模拟了球形颗粒在圆柱内的随机堆积，提出了计算床层径向孔隙率分布的方法。柱与颗粒直径比（N）在4至8之间变化，并且已经考虑了N→∞的两种单独的情况。颗粒雷诺数（Re d）从1到500变化。数值计算得到的压降和整体壁面到床层的传热系数为不同的模拟情况下进行了严格的比较与经验的相关性和一个很好的协议报告。此外，根据目前的数值计算结果，提出了关联式的压降和壁面到床层的传热系数。讨论了颗粒直径比（N）对流动和传热的影响，以及固液导热系数比对耦合传热的影响。此外，完全解析的精确数值模拟有助于阐明详细的孔尺度流动和传热特性的填充床。
A fully resolved direct numerical simulation of flow and heat transfer is presented for slender randomly packed bed reactors. The flow and temperature field are solved over a non-body fitted, non-conformal Cartesian computational domain. The coupling between fluid and solid (both spherical particles and cylindrical wall) is enforced by a second order accurate, sharp interface immersed boundary method (IBM). The present numerical technique neither requires any challenging volumetric mesh generation process nor demands manipulation of the geometry near the particle-particle and particle-wall contact points. Conjugate heat transfer has been considered where the temperature field is calculated both inside the solid particles and in the fluid. A discrete element method (DEM) is used to generate the random packings of spherical particles in the cylindrical column, and a methodology is proposed to calculate the radial porosity profile of the bed. The column-to-particle diameter ratio (N) is varied from 4 to 8, and two separate cases have been considered where N→∞. The particle Reynolds number (Re d) is varied from 1 to 500. The numerically obtained pressure drop and overall wall-to-bed heat transfer coefficient for different simulation cases are critically compared with empirical correlations and a good agreement is reported. Moreover, based on the current numerical results, correlations are proposed for the pressure drop and the wall-to-bed heat transfer coefficient. The effect of the column-to-particle diameter ratio (N) on both the flow and heat transfer, as-well-as the effect of the solid to fluid thermal conductivity ratio on the conjugate heat transfer are discussed. Furthermore, the fully resolved accurate numerical simulations have helped to elucidate the detailed pore-scale flow and heat transfer feature in the packed beds.