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See detailInvestigation of liquid flow morphology inside a structured packing using X-ray tomography
Janzen, Anna; Steube, Julia; Aferka, Saïd et al

in Chemical Engineering Science (2013), 12

In this work X-ray tomography is used to analyse the influence of liquid viscosity on liquid flow in a column filled with Mellapak Plus 752Y structured packing. Tomographic measurements are performed at ... [more ▼]

In this work X-ray tomography is used to analyse the influence of liquid viscosity on liquid flow in a column filled with Mellapak Plus 752Y structured packing. Tomographic measurements are performed at various column heights for different liquid flow rates. Water and glycerine aqueous solutions are successively used as working liquids in order to quantify the influence of liquid viscosity on hydrodynamic quantities such as liquid hold-up and gas-liquid interfacial area. As expected, both liquid hold-up and gas-liquid interfacial area increase with liquid flow rate. An increase of liquid viscosity has also a positive impact on liquid hold-up and on gas-liquid interfacial area. In all cases, the measured quantities are not constant along the bed height, leading to fluctuating axial profiles. Furthermore, tomographic images are used to identify different liquid flow patterns (films, contact-point liquid, flooded regions) in the irrigated cross section images. A method based on morphological techniques is proposed to quantify the fraction of liquid flow within each flow pattern depending on flow rate and liquid viscosity. [less ▲]

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See detailInvestigation of the influence of packing geometry and of liquid viscosity on the liquid flow morphology by using X-ray tomography
Janzen, Anna; Steube, Julia; Kenig, Evgeny et al

in Proceedings of the 7th World Congress on Industrial Process Tomography (2013)

X-ray tomography is used to investigate the influence of packing geometry and of liquid viscosity on hydrodynamic quantities, as well as on the liquid flow morphology inside a packed column successively ... [more ▼]

X-ray tomography is used to investigate the influence of packing geometry and of liquid viscosity on hydrodynamic quantities, as well as on the liquid flow morphology inside a packed column successively filled with two structured metallic packing, M752Y and M500X. As expected, liquid holdup and gas-liquid interfacial area increase with liquid flow rate and viscosity. In both packings, the film flow pattern predominates, while flooded regions remain minority. The influence of liquid flow rate and viscosity on flow morphology depends on the packing geometry. In M752Y, film and flooded region flows are clearly influenced, whereas in M500X, they are not. [less ▲]

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See detailModellierung des Trennverhaltens wässriger Systeme in Packungskolonnen basierend auf tomographischen
Janzen, Anna; Steube, Julia; Aferka, Saïd ULg et al

Conference (2012, March)

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See detailInvestigation of liquid flow pattern inside a structured packing using X-ray tomography
Aferka, Saïd ULg; Steube, Julia; Janzen, Anna et al

in Proceedings of the 6th International Symposium on Process Tomography, Cape Town, South Africa (2012)

This work focuses on the analysis of X-ray tomographic images of liquid flow distribution within a 1 m high packed column of 10 cm diameter, filled with four Mellapak Plus 752Y elements. Tomographic ... [more ▼]

This work focuses on the analysis of X-ray tomographic images of liquid flow distribution within a 1 m high packed column of 10 cm diameter, filled with four Mellapak Plus 752Y elements. Tomographic measurements are performed at various column heights for different liquid flowrates. Water and aqueous glycerine solutions are successively used as working liquids in order to quantify the influence of liquid viscosity on the spatial distribution of hydrodynamic quantities such as liquid holdup and gas-liquid interfacial area. Logically, both liquid holdup and gas-liquid interfacial area increase with liquid flow rate. An increase of liquid viscosity has also a positive impact on liquid holdup and on gas-liquid interfacial area. In all cases, the measured quantities are not constant along the bed height, leading to fluctuating axial profiles. Depending on the liquid viscosity and flowrate, different liquid flow patterns (films, rivulets, flooded channels) are observed in the irrigated cross section images. A method based on morphological techniques is proposed to quantify the fraction of liquid flow which belongs to each flow pattern. [less ▲]

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See detailMesure par tomographie à rayons X de l’influence de la viscosité sur la distribution du liquide dans une colonne à empilage structuré.
Aferka, Saïd ULg; Steube, Julia; Janzen, Anna et al

in In SFGP (Ed.), Récents Progrès en Génie des Procédés - N° 101 - Des procédés au service du produit au coeur de l'Europe - Actes du XIIIème Congrès de la société Française de Génie des Procédés - Du 29 Nov. au 1er Décembre 2011 - Lille Grand Palais, FRANCE (2011, December)

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See detailSimulation d’un écoulement de gaz dans un empilage structuré par la méthode des réseaux de Boltzmann
Beugre, Djomice; Calvo, Sébastien ULg; Crine, Michel ULg et al

in SFGP (Ed.) Récents Progrès en Génie des Procédés - N° 101 - Des procédés au service du produit au coeur de l'Europe - Actes du XIIIème Congrès de la société Française de Génie des Procédés - Du 29 Nov. au 1er Décembre 2011 - Lille Grand Palais, FRANCE (2011, November 29)

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental ... [more ▼]

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental measurements and with known correlations. They are also compared with simulations using a classical CFD code. In all cases, the agreement is very good. An original method based on the simulated axial velocity profiles is proposed to caracterize the gas flow regime. [less ▲]

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See detailCaractérisation microstructurale de mousses polymères nanocomposites par microtomographie à rayons X
Plougonven, Erwan ULg; Tran, Minh Phuong ULg; Marchot, Pierre ULg et al

Poster (2011, November 29)

Les circuits électriques, fonctionnant à des fréquences de plus en plus élevées, sont responsables de l’augmentation de la pollution électromagnétique, et justifient le développement de blindages ... [more ▼]

Les circuits électriques, fonctionnant à des fréquences de plus en plus élevées, sont responsables de l’augmentation de la pollution électromagnétique, et justifient le développement de blindages efficaces. De nombreuses applications sont concernées, que ce soit dans les systèmes électroniques commerciaux, industriels, ou militaires, ou les systèmes antennaires. Récemment, des blindages sous forme de composites polymère/charges carbonées ont été largement développés pour leur nombreux avantages : plus légers, moins chers, plus absorbants, et plus facilement moulables. Une charge carbonée prometteuse est le nanotube de carbone car de par son facteur de forme, une concentration moindre est nécessaire pour une conductivité équivalente [1]. Afin d’améliorer l’absorption de l’énergie électromagnétique de ces composites (par rapport à leur réflectivité), ils sont moussés pour réduire leur constante diélectrique. Cette étape de moussage doit être rigoureusement contrôlée pour atteindre le niveau d’absorption ciblé. Deux techniques de moussage sont envisagées dans cette étude, à savoir le moussage en CO2 supercritique (par imprégnation de CO2 en condition supercritique, avant une dépressurisation rapide) et le freeze-drying (dissolution dans un solvant, suivi d’une lyophilisation de celui-ci). Ces deux méthodes génèrent des structures de porosité bien distinctes, avec une anisotropie apparente marquée dans le second cas. L’objectif est de caractériser ces structures par tailles moyennes de pores et mesures d’anisotropie, et leur lien avec l’efficacité de blindage. Dans cette optique, la caractérisation est effectuée par microtomographie à rayons X, une technique d’imagerie 3D non-destructive. Des acquisitions sont faites sur chaque échantillon, et la microstructure est analysée par traitement d’images. Vu la très faible atténuation des rayons X dans ce type de matériaux, et la limite de résolution de cette technique par rapport à la taille des pores et à l’épaisseur des parois, la séparation précise des pores par rapport à la matrice polymère s’avère difficile. Une segmentation classique n’étant pas applicable en préalable à des mesures quantitatives, la fonction d’autocorrélation est utilisée. Cette technique, habituellement utilisée en traitement du signal, est une méthode performante de mesure globale de l’anisotropie d’un matériau [2]. Elle permet également d’extraire une longueur caractéristique qui peut être liée à la taille des cellules. Les résultats mettent en évidence l’impact de la technique et des conditions de moussage sur la microstructure des mousses composites. [less ▲]

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See detailGas Flow Simulations in a Structured Packing by Lattice Boltzmann Method
Beugre, Djomice; Calvo, Sébastien ULg; Crine, Michel ULg et al

Conference (2011, November 15)

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental ... [more ▼]

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental measurements and with known correlations. They are also compared with simulations using a classical CFD code. In all cases, the agreement is very good. [less ▲]

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See detailMicrostructure characterisation of nanocomposite polymeric foams by X-ray microtomography
Plougonven, Erwan ULg; Marchot, Pierre ULg; Detrembleur, Christophe ULg et al

Poster (2011, September 21)

Recent advances in microstructured materials have given rise to many new types of composites that exhibit original and interesting physical properties. For example, a nanocomposite made of carbon ... [more ▼]

Recent advances in microstructured materials have given rise to many new types of composites that exhibit original and interesting physical properties. For example, a nanocomposite made of carbon nanotubes inside a polymer matrix shows exceptional electromagnetic interference shielding effectiveness when foamed. However, the effective properties of such materials strongly depend on the shape and topology of the microstructural cells. An accurate method for investigating the cellular microstructure is X-ray microtomography (XRµT), for it is non-destructive, and it provides 3D geometric information. Although it cannot be used to observe nanofiller dispersion, it has a strong potential for cell structure characterization. In order to reduce the need for trial and error for tailoring these materials, our objective is to characterize, using XRµT, two different types of foaming procedures, namely supercritical CO2 batch foaming and freeze drying. As the resolution is limited compared to cell size, we have developed a novel statistical method based on 3D autocorrelation to determine characteristic length and examine anisotropy. We present results for these two types of foams and show the limitations of this method. [less ▲]

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See detailMethodology for the characterization of the microstructure of nanocomposite polymeric foams using X-ray microtomography
Plougonven, Erwan ULg; Marchot, Pierre ULg; Detrembleur, Christophe ULg et al

in Micro-CT User Meeting Abstract Book (2011, April 13)

Polymeric foams used in electromagnetic shielding applications are characterized using X-ray microtomography. These foams contain a conductive nanometric reinforcement, carbon nanotubes, but the scale of ... [more ▼]

Polymeric foams used in electromagnetic shielding applications are characterized using X-ray microtomography. These foams contain a conductive nanometric reinforcement, carbon nanotubes, but the scale of characterization described here is that of the microscopic cells. Although nanotube dispersion is important for the final properties of the material, the structure and distribution of the porosity also play a role in terms of dielectric constant and conductivity. Unfortunately, cell wall thinness and limited resolution of laboratory microtomographs makes poper cell identification difficult. Therefore we present a new statistical method based on the 3D autocorrelation function, that allows to some extent to measure mean cell size and structure anisotropy. [less ▲]

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See detailX-ray CT study of the influence of liquid viscosity on fluid phase distribution in modular catalytic packings
Aferka, Saïd ULg; Viva, Aurora; Brunazzi, Elisabetta et al

in Chemical Engineering Transactions (2011), 24

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an ... [more ▼]

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an aqueous solution of glycerine, the viscosity of which equals 10 cP, are used as feed liquids. The estimation of liquid holdup is of great interest due to its strong influence on pressure drop, on solid wetting and on heat and mass transfer coefficients. The experimental technique used is high energy X-ray tomography, which is a unique technique to visualize the local liquid distribution inside the complex structure of packings and to quantify the liquid holdup at different scales. [less ▲]

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See detailLattice Boltzmann Simulation Code Optimization Based on Constant-time Circular Array Shifting
Dethier, Gérard ULg; de Marneffe, Pierre-Arnoul ULg; Marchot, Pierre ULg

in Procedia Computer Science (2011), 4

Lattice Boltzmann (LB) methods are a class of Computational Fluid Dynamics (CFD) methods for fluid flow simulation. LB simulation codes have high requirements regarding memory and computational power ... [more ▼]

Lattice Boltzmann (LB) methods are a class of Computational Fluid Dynamics (CFD) methods for fluid flow simulation. LB simulation codes have high requirements regarding memory and computational power: they may involve the update of several millions of floating point values thousands of times and therefore require several gigabytes of available memory and run for several days. Optimized implementations of LB methods minimize these requirements. An existing method based on a particular data layout and an associated implementation implying a constant time array shifting allows to reduce the execution time of LB simulations and almost minimize memory usage when compared to a naive implementation. In this paper, we show that this method can be further improved, both in memory usage and performances by slightly modifying the data layout and by using blocking in order to enhance data locality. [less ▲]

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See detailGas Flow Simulations in a Structured Packing by Lattice Boltzmann Method
Beugre, Djomice; Calvo, Sébastien ULg; Crine, Michel ULg et al

in Chemical Engineering Science (2011), 66

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental ... [more ▼]

Numerical simulations of gas flow between two sheets of plastic MellapakTM 250 Y are performed using Lattice Boltzmann methods in laminar and turbulent regimes. Results are compared with experimental measurements and with known correlations. They are also compared with simulations using a classical CFD code. In all cases, the agreement is very good. [less ▲]

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See detailTomographic measurement of liquid hold up and effective interfacial area distributions in a column packed with high performance structured packings
Aferka, Saïd ULg; Viva, Aurora; Brunazzi, Elisabetta et al

in Chemical Engineering Science (2011), 66

In this paper, we report on the use of a high energy and high resolution X-ray tomograph to visualize and quantify the distribution of liquid hold up and of gas-liquid interfacial area in a 0.1m diameter ... [more ▼]

In this paper, we report on the use of a high energy and high resolution X-ray tomograph to visualize and quantify the distribution of liquid hold up and of gas-liquid interfacial area in a 0.1m diameter column filled with MellapakPlus 752.Y packing elements. A standard air-water system at room temperature and atmospheric pressure was used. Tomographic measurements have been carried out in a large number of packing cross sections situated at different heights between the top and the bottom of the packed column, giving access to the evolution of axial profiles of liquid hold up and of gas-liquid interfacial area as a function of the operating conditions. Gas-liquid interfacial area values were also measured by a chemical method (CO2 absorption from air into a caustic solution). For the first time, a whole set of gas-liquid interfacial area values evaluated from tomographic images are interestingly compared with values measured by a chemical method. A comparison is also presented with literature models. [less ▲]

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See detailDetermination of liquid hold-up and flow distribution inside modular catalytic structured packings
Viva, Aurora; Aferka, Saïd ULg; Toye, Dominique ULg et al

in Chemical Engineering Research & Design : Transactions of the Institution of Chemical Engineers Part A (2011), 89

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information ... [more ▼]

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information has been gathered at local scale by means of a non-intrusive high energy X-ray tomograph. Measurements have been carried out in a large number of packing cross sections situated at different heights between the top and bottom of the packed column, giving access to the evolution of axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) as a function of the liquid load. The total hold-up, evaluated by averaging local tomographic values over the packed volume, was compared with global hold-up data obtained by traditional methods, like draining and RTD measurements. A method was also proposed to deduce the distribution of liquid flowrate, between the reaction and the separation zones, from hold-up distribution measured by tomography. The methodology was validated by comparison with experimental data obtained by collecting separately the liquid flowing out of the two zones at the bottom of the packed bed. The obtained results are invaluable to improve the description of hydrodynamics in rate based performance models. [less ▲]

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See detailProcessing of X-ray tomographic images: a procedure adapted for the analysis of phase distribution in MellapakPlus 752.Y and Katapak-SP packings
Viva, Aurora; Aferka, Saïd ULg; Brunazzi, Elisabetta et al

in Flow Measurement & Instrumentation (2011), 22

We developed a simple practical methodology to face common problems encountered in the analysis of tomographic images to get quantitative information on phase distributions in gas liquid contacting ... [more ▼]

We developed a simple practical methodology to face common problems encountered in the analysis of tomographic images to get quantitative information on phase distributions in gas liquid contacting columns packed with complex metallic packings. In particular, the procedure (thresholding and normalisation) was developed and validated on images of geometrically well known Mellapak Plus 752 Y packings. The methodology was extended to images of Katapak-SP modular packings which are made of an alternation of Mellapak Plus 752 Y sheets and catalytic baskets. Global liquid hold-up, obtained by averaging tomographic results over the column height, were found in agreement with bed scale data measured on the same Mellapak Plus 752 Y and Katapak-SP (11 and 12) packings at a given liquid load. Moreover, gas-liquid interfacial area were calculated and reported to the installed geometric area. [less ▲]

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See detailX-ray tomography : a key for revealing local behavior of fluids in packed beds
Toye, Dominique ULg; Marchot, Pierre ULg; Crine, Michel ULg

Scientific conference (2010, October 28)

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See detailInfluence of medium composition on oxygen transfer rate in animal cell culture
Toye, Dominique ULg; Galifi, A.; Salmon, Thierry ULg et al

in Canadian Journal of Chemical Engineering (2010), 88(4), 671-676

Experiments were conducted in a 0.25m diameter bubble column to investigate the effect of medium composition on oxygen transfer rate. Aqueous solutions, the composition of which mimics a mammalian cell ... [more ▼]

Experiments were conducted in a 0.25m diameter bubble column to investigate the effect of medium composition on oxygen transfer rate. Aqueous solutions, the composition of which mimics a mammalian cell culture medium, are used. The effect on oxygen transfer rate of additives used to protect cells against local hydrodynamic stresses induced by bubble coalescence and bursting is addressed, in the range of operating conditions (aeration rates) met in animal cell cultures. The mass transfer coefficient, the liquid viscosity and surface tension, and the bubble size distribution are measured as a function of liquid composition and of gas superficial velocity, allowing to decouple the effects of the different additive on kL and on a. [less ▲]

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See detailLiquid load point determination in a reactive distillation packing by x-ray tomography
Aferka, Saïd ULg; Viva, Aurora ULg; Brunazzi, Elisabetta et al

in Canadian Journal of Chemical Engineering (2010), 88(4), 611-617

In this paper, we report on the use of Xray tomography to determine the liquid load point in 0.1m diameter modular catalytic distillation packings KatapakSP11 and KatapakSP12. The liquid load point ... [more ▼]

In this paper, we report on the use of Xray tomography to determine the liquid load point in 0.1m diameter modular catalytic distillation packings KatapakSP11 and KatapakSP12. The liquid load point corresponds to the overall packed bed liquid load above which there is an increment in the liquid flowing outside the catalytic baskets and the catalytic baskets themselves are saturated with liquid. From tomographic images, we show that several factors affect the wetting and filling of catalytic baskets. The complex hybrid structure of catalytic packings influences the liquid distribution inside the elements. The liquid preferentially fills the external catalytic baskets because they receive the liquid not only from the packing element situated above but also from the wall wipers. Moreover, liquid holdup inside a catalytic basket section depends significantly on the vertical position in the packing element and on the position of the packing in the column packed bed. The counter–current gas flow speeds up the process of liquid filling of the baskets, also for low liquid loads. The nonuniform distribution of liquid in catalytic basket which is observed experimentally makes the identification of a unique liquid load point not straightforward. [less ▲]

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