Pore-Scale Simulation for the Fully-Developed Flow Through a Fixed-Bed Reactor Regularly Packed with Mono-Sized Spheres with Extension to Random Packing

IF 2.7 3区 工程技术 Q3 ENGINEERING, CHEMICAL
Liang-Ching Cheng, Shwin-Chung Wong
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引用次数: 0

Abstract

This work conducts pore-scale numerical computations to reveal the hydrodynamic characteristics of the fully-developed flow through a fixed-bed reactor regularly packed with mono-sized spheres. One of the main purposes is to obtain invariant standard values which can be used as the benchmarks for those results from randomly packing methods such as Monte Carlo or DEM. Also, a repeatable and verifiable process is introduced to forecast the pressure drop and the mass flow rate in a packed bed without running any numerical simulation.

The mono-sized spheres in the present simulations are in FCC, BCC, or SC arrangement. For each packing, different Reynolds numbers and lattice angles are considered. For these regular arrangements, it is revealed that the cross-section of the reactor can be clearly separated into two regions: the more loosely-packed near-wall region and the densely-packed core region, with a boundary at a half-sphere diameter distance from the wall. The mass flow rates into the two regions will self-adjust themselves in proportion. Consequently, separate average Reynolds numbers in the near-wall, Rew, and the core region, Reco, are defined. Comparison of our computational results for fully-developed conditions with the experimental data for regular packings is presented. However, the inevitable presence of the entrance effect in the experiments on insufficiently-long regular packed beds forbids pertinent comparison. This work then continues to present a simplified model to predict the pressure drop through a reactor randomly packed with mono-sized spheres. The empirical correlations of CD \(\times\) d/L with Rew or Reco in respective regions are derived. These correlations can be used to evaluate the pressure drop through a reactor at a given total mass flow rate, which is proportioned in each region. A linear interpolation or extrapolation procedure is proposed to evaluate the \(\Delta\) P based on the \((1/\Delta\) PFCC)-\({\varepsilon }_{\text{FCC}}\), \((1/\Delta P\text{BCC}\))-\({\varepsilon }_{\text{BCC}}\), and \((1/\Delta\) PSC)-\({\varepsilon }_{\text{SC}}\) relations, with given average void fraction \(\varepsilon\), diameter and length of the container, particle diameter, and total mass flow rate. The reliability of the simplified model has been validated through the comparison with empirical correlations and Monte Carlo simulation in the literature.

Abstract Image

Abstract Image

固定床反应器中规则填料单粒径球体的充分发展流动的孔隙尺度模拟,并扩展至随机填料
这项工作进行了孔隙尺度数值计算,以揭示流经固定床反应器的完全发展流的流体力学特征,该反应器规则地填满了单尺寸球体。主要目的之一是获得不变的标准值,这些值可作为蒙特卡罗或 DEM 等随机填料方法得出的结果的基准。此外,还引入了一个可重复、可验证的过程,在不运行任何数值模拟的情况下预测填料床中的压降和质量流量。对于每种填料,都考虑了不同的雷诺数和晶格角度。对于这些规则排列,可以发现反应器的横截面可明显分为两个区域:堆积较松散的近壁区域和堆积较密集的核心区域,其边界位于距壁半球直径的距离处。进入这两个区域的质量流量将按比例自行调整。因此,近壁区域 Rew 和核心区域 Reco 的平均雷诺数是分开定义的。我们将完全膨胀条件下的计算结果与常规填料的实验数据进行了比较。然而,由于在长度不足的规则填料床实验中不可避免地存在入口效应,因此无法进行相关比较。随后,这项工作继续提出了一个简化模型,用于预测通过随机填满单尺寸球体的反应器的压降。得出了 CD \(\times\) d/L 与相应区域的 Rew 或 Reco 的经验相关性。这些相关关系可用于评估在给定总质量流量下通过反应器的压降,而总质量流量在每个区域都是成比例的。建议使用线性内插法或外推法来评估基于 \((1/\Delta\) PFCC)-\({\varepsilon }_{text/{FCC}}\)、\((1/\Delta Ptext\{BCC\}))-\({\varepsilon }_{text/{BCC}}\)、\((1/\Delta Ptext\{BCC\}))-\({\varepsilon }_{text/{BCC}}\)的 P、和 \((1/\Delta\) PSC)-\({\varepsilon }_{text/{SC}}\)关系,给定平均空隙率 \(\varepsilon/)、容器直径和长度、颗粒直径和总质量流量。通过与文献中的经验相关性和蒙特卡罗模拟进行比较,验证了简化模型的可靠性。
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来源期刊
Transport in Porous Media
Transport in Porous Media 工程技术-工程:化工
CiteScore
5.30
自引率
7.40%
发文量
155
审稿时长
4.2 months
期刊介绍: -Publishes original research on physical, chemical, and biological aspects of transport in porous media- Papers on porous media research may originate in various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering)- Emphasizes theory, (numerical) modelling, laboratory work, and non-routine applications- Publishes work of a fundamental nature, of interest to a wide readership, that provides novel insight into porous media processes- Expanded in 2007 from 12 to 15 issues per year. Transport in Porous Media publishes original research on physical and chemical aspects of transport phenomena in rigid and deformable porous media. These phenomena, occurring in single and multiphase flow in porous domains, can be governed by extensive quantities such as mass of a fluid phase, mass of component of a phase, momentum, or energy. Moreover, porous medium deformations can be induced by the transport phenomena, by chemical and electro-chemical activities such as swelling, or by external loading through forces and displacements. These porous media phenomena may be studied by researchers from various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering).
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