The Measurement of Void Fraction Profiles in Packed Beds

Lerou, Jan; Froment, Gilbert F.

doi:10.1007/978-94-009-4400-8_18

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…A family of curves is obtained, with the ratio alb as a parameter; the curves show similar behaviour to the solid cylinders case. Previous work (England and Gunn, 1970;Lerou and Froment, 1986) is again in good agreement with present results.…”

Section: Resultssupporting

confidence: 94%

“…T used to characterize the packing in a fixed bed (Haughey and Beveridge, 1969). Although much recent work has been directed towards measurement of radial void fraction profiles (see, for example, Lerou and Froment (1986)), such profiles are not generally incorporated into correlations for design variables and transport properties such as pressure drop and heat transfer coefficients. Rather it is the single bulk void fraction that is used, and the correlations for pressure drop in particular are sensitive to the void fraction value.…”

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confidence: 99%

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Correlations for wall and particle shape effects on fixed bed bulk voidage

Dixon¹

1988

Can J Chem Eng

206

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Correlations have been derived, by both geometrical arguments and empirical treatment of data, for the bulk void fraction in a fixed bed. The void fraction has been correlated as a function of particle‐to‐tube diameter ratio for packings of spheres and equilateral solid cylinders. Prediction of void fraction for equilateral hollow cylinders can be made from the solid cylinder correlation, provided a correction factor is included that allows for internal voidage and interpenetration of packings.

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Section: Resultssupporting

confidence: 94%

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confidence: 99%

Correlations for wall and particle shape effects on fixed bed bulk voidage

Dixon¹

1988

Can J Chem Eng

206

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“…In the design and analysis of equipment where wall effects are significant, local porosity distribution, in both the radial and axial directions, is often utilised to provide a more detailed insight into packing structure. Past studies investigating the local characteristics of sphere and cylinder packed beds include using experimental methods (Ridgway and Tarbuck, 1968;Gotoh et al, 1978;Lerou and Froment, 1986;McGreavy et al, 1986;Zou and Yu, 1996;Ismail et al, 2002;Di Felice and Gibilaro, 2004), analytical means (Moallemi, 1989;Papageorgiou and Froment, 1995;Afandizadeh, 1996;Wang et al, 2001) and empirical correlations (Martin, 1978;Cohen and Metzner, 1981;Dixon, 1988;Kubie, 1988;Mueller, 1992;Foumeny et al, 1993). Additionally, information on the packing of more complex pellet shapes (e.g.…”

Section: Introductionmentioning

confidence: 99%

Digital predictions of complex cylinder packed columns

Caulkin

Ahmad

Fairweather

et al. 2009

Computers & Chemical Engineering

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A digital computational approach has been developed to simulate realistic structures of packed beds. The underlying principle of the method is digitisation of the particles and packing space, enabling the generation of realistic structures. Previous publications (Caulkin et al., 2006(Caulkin et al., , 2007 have demonstrated the ability of the code in predicting the packing of spheres. For cylindrical particles, however, the original, random walk-based code proved less effective at predicting bed structure. In response to this, the algorithm has been modified to make use of collisions to guide particle movement in a way which does not sacrifice the advantage of simulation speed. Results of both the original and modified code are presented, with bulk and local voidage values compared with data derived by experimental methods. The results demonstrate that collisions and their impact on packing structure cannot be disregarded if realistic packing structures are to be obtained.

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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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The Measurement of Void Fraction Profiles in Packed Beds

Cited by 5 publications

References 21 publications

Correlations for wall and particle shape effects on fixed bed bulk voidage

Correlations for wall and particle shape effects on fixed bed bulk voidage

Digital predictions of complex cylinder packed columns

Review on the structure of random packed‐beds

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