Visualisation of flow processes in packed beds with NMR imaging: determination of the local porosity, velocity vector and local dispersion coefficients

Götz, Joachim; Zick, Klaus; Heinen, Claudia; König, Thomas

doi:10.1016/s0255-2701(01)00185-4

Cited by 40 publications

(20 citation statements)

References 45 publications

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“…This demonstrates that in such a fixed bed with low aspect ratio the void fraction is higher near the tube wall than inside the packing. This observation is in agreement with the Laser Doppler Anemometry results of similar packed beds [25].…”

Section: Characterization Of the Bed Structuressupporting

confidence: 93%

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Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Ren

Stapf

Blümich

2005

Chem. Eng. Technol.

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Different NMR techniques were combined to obtain the structure and velocity information for a systematic investigation of fixed beds with low aspect ratio (tube diameter to particle diamter, d t /d p ) in the range 1.4 to 32. The structure of the void space was determined for a variety of packed beds of glass beads or regular and irregular porous pellets by magnetic resonance imaging (MRI). Based on the images the radial distribution of the voids within the bed was obtained. Ordering effects were found even for non-spherical and polydisperse particles, and a maximum of the fluid density near the tube wall was confirmed for all pellet geometries and sizes. By combining MRI with velocity encoding, velocity profiles and distributions of flow velocity components of a single fluid phase through packed beds have been acquired. The radial velocity distribution follows an oscillatory pattern which largely reflects the ordering of the particles, which can be accessed from the density distribution of the interparticle fluid. Maximum velocities of up to four times the average value were found to occur near the tube wall. This wall effect was observed for all but the smallest particles, where the aspect ratio was d t /d p = 32. Moreover, a visualisation of flow pattern in the presence of packed particles was achieved by using a tagging technique, and the stationary flow field could be identified for an experimental time of several hours.

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Section: Characterization Of the Bed Structuressupporting

confidence: 93%

“…2). This result is in good agreement with the results of Götz et al [25] and Feinauer [26]. The experimental velocity maxima determined by NMR are almost at the same position as the maxima determined from modeling d /d = 32 [1,27] and by anemometry [4] for a similar aspect ratio.…”

Section: Velocity Distributionsupporting

confidence: 91%

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Ren

Stapf

Blümich

2005

Chem. Eng. Technol.

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“…In spite of PVA single oil drops can be detected at the wall. The length of the oil drops and plugs, respectively, is between three and four tube diameters D. Besides single oil drops (AE » 0.5 D) ªmoving packed bedsº of oil drops (AE » 0.1±0.2 D) appear, where water flows through the oil drops like through a packed bed [41]. The emulsion is not stable, as sedimentation, aggregation and coalescence occur with increasing convey distance.…”

Section: Resultsmentioning

confidence: 99%

“…Sv/v has values of the same order of magnitude in the flow through a packed bed [41]. The high values for a flow rate of 100 mL/s might suggest that the flow-induced structure of a water/oil mixture is similiar to a packed bed which is not built up by rigid packing material, but by deformable oil drops.…”

Section: Velocity Componentsmentioning

confidence: 99%

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Local Velocity and Concentration of the Single Components in Water/Oil Mixtures Monitored by Means of MRI Flow Experiments in Steady Tube Flow

Götz¹,

Zick

2003

Chem Eng & Technol

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In this paper the spatially resolved determination of velocities in two-phase systems consisting of water and oil by means of nuclear magnetic resonance (NMR) imaging (MRI) techniques is described and applied to steady tube flows with regard to the total flow rate. As MRI offers the possibility to study the flow of multiphase materials spatially resolved with various forms of contrast, even optically opaque water/oil mixtures can be studied in the interior of the material. Besides snapshot images of the actual flow pattern also local velocity and concentration fields of both phases can be obtained separately. The insight into the inner micro flow processes and microstructure allows to characterize fluid mixtures or emulsions. Flow rate and preparation/ mixing method were varied in order to realize changes of the flow pattern and the structure of the mixture during flow. Physical models of the flow behavior and physical stability of these complex systems can be based upon this information.

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Recent Advances in TES Methods, Technologies, and Applications

Dinçer

Rosen

2010

Thermal Energy Storage

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Visualisation of flow processes in packed beds with NMR imaging: determination of the local porosity, velocity vector and local dispersion coefficients

Cited by 40 publications

References 45 publications

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Local Velocity and Concentration of the Single Components in Water/Oil Mixtures Monitored by Means of MRI Flow Experiments in Steady Tube Flow

Recent Advances in TES Methods, Technologies, and Applications

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