A fluorescence method for the measurement of the local voidage in random packed beds

Buchlin, Jean‐Marie; Riethmuller, M. L.; Ginoux, Jean J.

doi:10.1016/0009-2509(77)80153-x

Cited by 11 publications

(10 citation statements)

References 9 publications

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“…The specification of the blackwhite threshold is frequently identified as the major source of error. Additionally, Buchlin et al, [129] whose work was later adopted by Schneider and Rippin, [102] used the fluorescence of a slightly impure organic liquid having the same refractive index as transparent spheres to visualize the particle locations. Besides X-ray tomography, magnetic resonance imaging may be used as well to investigate local structures within packedbeds.…”

Section: Methodsmentioning

confidence: 99%

Review on the structure of random packed‐beds

Seckendorff

Hinrichsen

2021

Can J Chem Eng

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Independent from their intended purpose, the understanding of structural characteristics of random packings of particles having defined shapes is important to understand and optimize fluid dynamic behaviour, heat, and mass transfer. The packing structure can be described by the coordination number, local porosity profiles, the average porosity, and pore characteristics, which are influenced by the wall and thickness effect; the material, shape, and size distribution of the packing particles; the packing and compaction mode; and the shape and material of the packing's containing walls. Therefore, existing knowledge on the structure of randomly packed mono-sized particles is reviewed to provide an updated selection of relevant parameters and their derived correlations obtained by experimental, numerical, and analytical means.packed-bed reactor, porosity, random particle packings, review, structure | INTRODUCTIONRandom packings of particles having defined shapes are deployed in all kinds of industrial applications and come in all orders of magnitude. The most prominent examples comprise micro-sized particle beds as commonly used in chromatography packed columns, [1][2][3] packed-bed reactors filled with catalytic shaped bodies having millimetre size, [4,5] packed columns used in separation processes such as distillation incorporating particles in the lower centimetre range, [6,7] and the pebble-bed reactor, which is a gas-cooled nuclear reactor, moderated by a packing of graphite spheres. [8][9][10] In addition to those, numerous less-known applications of packed-beds exist, ranging from powder-bed 3D printers, [11] solar-energy storage systems, [12] earth science, [13] civil engineering, [14,15] and pharmaceutical processing, [16] to the pyrolysis of pelletized wood fuels, [17] to name but a few.Irrespective of its intended purpose, the extent of a packed-bed is limited by a confining wall of commonly cylindrical shape, though flat plates and other container geometries are possible. Despite its generally random nature, close to this confinement the particles' placement is naturally forced to align with the wall's geometry. This imposed order reaches a couple of particle diameters into the packing and is usually named the wall effect. Its influence on the overall packed-bed characteristics decreases with increasing tube-to-particle diameter ratio λ = D d p . While most applications operate in an only sparsely affected λ-range, this effect becomes dominant, for instance, in catalytic multitubular reactors, typically performing at λ = 4-7 [18] or a single-pellet-string reactor with a λ < 2. [19] Moreover, some packed-bed utilizations, especially chromatography columns, have very delicate requirements regarding bed homogeneity and its derived characteristics.Abbreviations: DEM, discrete element method; Erfc, error function; J 0 , Bessel function of first kind and zero order; MRJ, maximally random jammed; RCP, random close packing; RLP, random loose packing.

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Section: Methodsmentioning

confidence: 99%

Review on the structure of random packed‐beds

Seckendorff

Hinrichsen

2021

Can J Chem Eng

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“…This procedure was repeated several times, until a statistical analysis was possible. An other method by Buchlin et al, [19] is based on the fluorescence of a slightly impure organic liquid and on the refractive index matching of the packing particles. The method requires the use of particles made of a transparent material.…”

Section: Experimental Equipmentmentioning

confidence: 99%

The Measurement of Void Fraction Profiles in Packed Beds

Lerou

Froment

1986

Chemical Reactor Design and Technology

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“…'^^' Equation (9) and others like it allows us to construct the working field equations for each phase using fixed (Eulerian) control volumes on the order of the size eg,. '38' The dispersed phases may consist of shale particles when the continuous phase is a vapor.…”

Section: Continuum Equation Proceduresmentioning

confidence: 99%

“…The concept of domains allows the writing of mass and energy equations for each identifiable collection of oil shale particle^. '^^' Equation (9) and others like it allows us to construct the working field equations for each phase using fixed (Eulerian) control volumes on the order of the size eg,. For example, the accumulation of the total amount of vapor mass, M, in V = eSm, is given by -…”

Section: Continuum Equation Proceduresmentioning

confidence: 99%

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Modeling of flow nonuniformities in fissured porous media

Lyczkowski¹

1982

Can J Chem Eng

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A review is performed to.trace how fissured porous media arise in nature. It is fourid that packed beds resemble fissured porous media. The range of multiple flow time-scales inherent in such media becomes larger as the particle size range becomes broader, resulting in flow nonuniformities. The status of experimental measurements of voidage and flow nonuniformities is assessed. Some of the difficulties associated with modeling of the multiple flow time-scales are discussed, and a tentative model is proposed.acked beds a r e frequently used a s energy con-P verters in fossil and nuclear related industries.They are used in the catalytic reforming of petroleum, in the gasification of coal, in high-temperature gascooled pebble-bed nuclear reactors and in the retorting of oil shale. Considering the demand f o r fossil fuels, the efficient and safe operation of these energy converters is important to maximize recovery. Channeling and by-passing caused by nonuniform flow prodwe hot spots indicative of runaway reactions and combustion of valuable products. This paper shows that real packed beds resemble fissured porous media since even so-called random packing results in non-random voidage variations and flow structures. Even small voidage variations cause considerable flow nonuniformities" that can produce a highly dispersive system."' Later sections discuss the basic difficulty associated with modeling flow in fissured porous media having a multiplicity of time-scales. A tentative flow model that uses multi-phase flow concepts is suggested. How fissured porous media and flow nonuniformities arise in natureFigure 1 illustrates the basic concept of a fissured porous m e d i~m . '~' The figure, which appeared in a n article by Bear and Braester who attributed it to the Soviet Barenblatt,'4,'J shows a network of interconnecting gaps or fissures, in between which a r e regions called porous blocks containing characteristically smaller gaps. Such a situation might arise from fracturing of tight sands for t h e recovery of unconventional natural gas, f o r example. Flows through t h e smaller gaps are called porous-media flows, while flows through the larger gaps are called fissure flows. Hence the flow field has overlapping continua with exchange of fluid between the fissures and the porous block. This fissured porous medium On a fait une revue de littirature sur l'origine naturelle de la fissuration des milieux poreux; on a trouvt que les lits garnis prtsentent une certaine ressemblance avec ces milieux. La gamme des temps d'hcoulements multiples inhtrents aux milieux en question s'hlargit A mesure que celle des dimensions des particules s'accroft et il en rksulte un manque d'uniformitk dans les kcoulements. On a fait le point de ]'&at de la question des mesures expkrimentales du degrt de vide et des manques d'uniformitt des hcoulements. On discute quel- ques-unes des difficultbs de modblisation des temps mis en jeu dans les icoulements multiples et on propose un modhle a vtrifier.representation is a simplification of much ...

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A fluorescence method for the measurement of the local voidage in random packed beds

Cited by 11 publications

References 9 publications

Review on the structure of random packed‐beds

Review on the structure of random packed‐beds

The Measurement of Void Fraction Profiles in Packed Beds

Modeling of flow nonuniformities in fissured porous media

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