Effect of Tube-to-Pellet Diameter Ratio on Turbulent Hydrodynamics in Packed Beds: A Magnetic Resonance Velocity Imaging Study

IF 1.1 4区 物理与天体物理 Q4 PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
Scott V. Elgersma, Andrew J. Sederman, Michael D. Mantle, Constant M. Guédon, Gary J. Wells, Lynn F. Gladden
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引用次数: 0

Abstract

The hydrodynamics in packed reactors strongly influences reactor performance. However, limited experimental techniques are capable of non-invasively measuring the velocity field in optically opaque packed beds at the turbulent flow conditions of commercial relevance. Here, compressed sensing magnetic resonance velocity imaging has been applied to investigate the hydrodynamics of turbulent flow through narrow packed beds of hollow cylindrical catalyst support pellets as a function of the tube-to-pellet diameter ratio, \(N\), for \(N=\) 2.3, 3.7, and 4.8. 3D images of time-averaged velocity for the gas flow through the beds were acquired at constant Reynolds number, \(R{e}_{\mathrm{p}}=\) 2500, at a spatial resolution of 0.70 mm (\(\tt x\)) \(\times\) 0.70 mm (\(\tt y\)) \(\times\) 1.0 mm (\(\tt z\)). The resulting flow images give insight into the bed and pellet scale hydrodynamics, which were systematically compared as a function of \(N\). Some changes in hydrodynamics with \(N\) were observed. Namely, the near-wall hydrodynamics changed with \(N\), with the \(N=\) 4.8 bed showing higher velocity at the wall compared to the \(N=\) 2.3 and \(N=\) 3.7 beds. Further, in the \(N=\) 3.7 bed, channels of high velocity, termed flow lanes, were found 1.3 particle diameters from the wall, possibly due to the bed structure in this particular bed. At the pellet scale, the hydrodynamics were found to be independent of \(N\). The results reported here demonstrate the capability of magnetic resonance velocity imaging for studying turbulent flows in packed beds, and they provide fundamental insight into the effect of \(N\) on the hydrodynamics.

Abstract Image

管球直径比对充填床湍流流体动力学的影响:磁共振速度成像研究
填料反应器内的流体力学对反应器的性能影响很大。然而,有限的实验技术能够在与商业相关的湍流条件下无创地测量光学不透明填充床中的速度场。在这里,压缩传感磁共振速度成像已经被应用于研究湍流通过中空圆柱形催化剂支撑球团的狭窄填充床的流体动力学,作为管与球团直径比\(N\)的函数,\(N=\) 2.3, 3.7和4.8。在恒定雷诺数\(R{e}_{\mathrm{p}}=\) 2500下,以0.70 mm (\(\tt x\)) \(\times\) 0.70 mm (\(\tt y\)) \(\times\) 1.0 mm (\(\tt z\))的空间分辨率,获得了气体流过床层时平均速度的三维图像。由此产生的流动图像可以深入了解床层和球团尺度的流体动力学,并将其作为\(N\)的函数进行系统比较。观察到\(N\)对流体力学的影响。即,近壁流体力学随\(N\)的变化而变化,与\(N=\) 2.3和\(N=\) 3.7层相比,\(N=\) 4.8层在壁面处的速度更高。此外,在\(N=\) 3.7床层中,发现了高速通道,称为流道,距离壁面1.3颗粒直径,可能是由于这个特殊床层的床层结构。在颗粒尺度上,流体力学与\(N\)无关。本文的研究结果证明了磁共振速度成像研究充填床湍流的能力,并为研究\(N\)对流体力学的影响提供了基本的见解。
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来源期刊
Applied Magnetic Resonance
Applied Magnetic Resonance 物理-光谱学
CiteScore
1.90
自引率
10.00%
发文量
59
审稿时长
2.3 months
期刊介绍: Applied Magnetic Resonance provides an international forum for the application of magnetic resonance in physics, chemistry, biology, medicine, geochemistry, ecology, engineering, and related fields. The contents include articles with a strong emphasis on new applications, and on new experimental methods. Additional features include book reviews and Letters to the Editor.
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