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Papers by Christophe Boyer
Opérations unitaires. Génie de la réaction chimique
On propose une etude theorique et experimentale d'un procede de debitmetrie triphasique eau-h... more On propose une etude theorique et experimentale d'un procede de debitmetrie triphasique eau-huile-gaz. Le procede retenu repose sur l'utilisation conjointe d'un melangeur, d'un venturi et de methodes ultrasonores. La validation experimentale de ce procede a mis en jeu le dimensionnement, la conception et la mise au point d'un dispositif entierement instrumente pour les ecoulements triphasiques eau-huile-air. Un modele original d'ecoulement triphasique disperse a ete etabli. Une fois valide sur la base de resultats en ecoulement eau-air, eau-huile et eau-huile-air, ce modele a permis de resoudre les problemes de metrologie lies a l'utilisation du venturi en presence de ces ecoulements. Sur la base d'une analyse critique des techniques utilisables, la mesure de la vitesse de propagation ultrasonore a ete selectionnee pour determiner la composition des ecoulements liquide-liquide. Deux modeles originaux ont ete developpes pour decrire la propagation ultr...
CFD is used to study liquid spreading in gas-liquid co-current trickle-bed reactors using two-flu... more CFD is used to study liquid spreading in gas-liquid co-current trickle-bed reactors using two-fluid approach. In order to propose a model that describes exhaustively all interaction forces acting on each fluid phase as well as dispersion mechanisms, a discussion of closure laws available in literature is proposed. Liquid dispersion is recognized to result from two main mechanisms: capillary and mechanical. The proposed model is then implemented in two trickle-bed configurations matching with two experimental set ups (Boyer et al., 2005 and Marcandelli et al., 2000). In the first configuration, simulations on a 2D axisymmetric geometry are considered and the model is validated upon a new set of experimental data. Liquid distribution obtained from gamma−ray tomography is provided for different geometrical and operating conditions. In the second configuration, a 3D simulation is considered and the model is validated upon experimental liquid flux patterns at the bed outlet. A sensitivit...
Chemie Ingenieur Technik, 2001
Chemical Engineering Science, 2002
In the petrochemical industry area, many processes are carried out using ÿxed bed reactors with c... more In the petrochemical industry area, many processes are carried out using ÿxed bed reactors with cocurrent upward or downward gas=liquid ows. One of the main problems to overcome during the scale-up of such reactors is to optimize the gas=liquid ow distribution across the reactor catalytic bed section. To accurately characterize the gas=liquid ow distribution inside a real catalytic bed, a new computed gamma-ray tomographic system has been developed to investigate two-phase ow through cold mock-ups of large scale (60 cm in diameter). In the case of developing a new reactor technology for processes working with ÿxed bed in the trickling ow regime, this type of measurement is quite important. This system, unique for such a large size catalyst bed, includes a series of 32 BGO detectors and a Cs 137 source. The performances of this experimental system have been fully evaluated through a validation including reconstruction of physical phantoms in static conditions. Several tests have been performed to measure the gas=liquid ow distribution in the catalyst bed for di erent inlet distributor conÿgurations. It is shown, in the experiments performed for the trickle ow regime, that the instrumental technique has a very good sensitivity to liquid retention measurement. When the liquid retention measurements are compared with a hydrodynamic model based on Kozeny-Carman formalism a quantitative agreement is observed.
International Journal of Multiphase Flow, 1997
be easily determined using Newtonian fluids alone. It is shown that the Debex on-line viscometer ... more be easily determined using Newtonian fluids alone. It is shown that the Debex on-line viscometer gives flow curves very similar to a conventional laboratory viscometer when this procedure is applied.
HAL (Le Centre pour la Communication Scientifique Directe), May 30, 2010
Multiphase reactors operated in fixed bed configuration are widely used in petrochemical industry... more Multiphase reactors operated in fixed bed configuration are widely used in petrochemical industry but their hydrodynamic is still not well understood. In a previous paper (Bordas et al, 2006), a new one-dimensional model able to predict the pressure drop and the mean void fraction for bubbly flows in packed beds was proposed. The equations required closure laws accounting for the liquid-solid and the gas-liquid interactions. Compared to previous models, these laws had been completely revisited, in order to better account for the flow dynamics at the pore scale. In particular, it had been demonstrated that (i) in dilute conditions, the bubble size remains of the order of the pore (ii) and that the mean bubble dynamics is somewhat similar to that of a slug, with a relative velocity at meso-scale linearly increasing with the liquid superficial velocity. Besides, that relative velocity monotonically increases with the gas flow rate ratio, a behaviour that is tentatively attributed to the formation of preferential paths for the gas phase. (iii) Based on the motion of a bubble train in capillary tubes, the two-phase flow pressure drop f ls scaled by its single-phase flow counterpart f lsφ at the same superficial liquid velocity is predicted to linearly increase with the void fraction, with a prefactor λ evolving with the Capillary number: Ψ = f ls / f lsφ =1+λ(Ca)α. Considering the capillary pressure contribution to the pressure drop, one expects λ∼Ca-1/3 [Bretherton 1961]. These proposals were only partly validated and required further confirmation. Thus, new experiments have been performed at LEGI and at IFP in order to cover an enlarged range of flow conditions while gathering all the necessary information to test the model. Attention has been paid to the measuring techniques, both to understand the exact meaning of the measured quantities and to control the uncertainty. So far, the results confirm the postulated dynamic. The model presented assumes that all the bubbles contributing to the void fraction are mobile while in some circumstances, bubbles can be trapped within the bed. Fixed bubbles can also contribute to the pressure drop, and the closure proposed does not take such contributions into account, This question was addressed by way of a thorough data analysis. Data gathered on the void fraction and pressure loss shows that the proposed closures laws for the gas dynamic and two-phase flow pressure drop are still relevant for moderate pressure conditions (up to 10 bars) and gas volumetric ratio β ranging from 20% to 70%. In the range of operating conditions considered (capillary number, gas ratio β), bubbles-bubbles interactions probably limit such blockage. Those interactions would explain also why the size distribution remains controlled by the pore characteristic dimension, through a process of continuous coalescence/breakup. Using these closures, the model sensitivity was studied and its ability to predict the void fraction and pressure loss addressed.
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2010
Simulation numérique par CFD de l'hydrodynamique et des performances thermiques d'un micro échang... more Simulation numérique par CFD de l'hydrodynamique et des performances thermiques d'un micro échangeur de chaleur-Pour évaluer les performances et les limitations d'un échangeur thermique compact composé de plaques micro-structurées, des simulations CFD de l'hydrodynamique et des transferts thermiques ont été effectués en écoulement liquide/liquide pour un micro-échangeur commercialisé par l'IMM. Les résultats de la simulation hydrodynamique montrent que la distribution des flux de l'écoulement liquide est plutôt homogène avec quelques gradients de vitesses à l'entrée des canaux à cause d'effets inertiels dans le distributeur. Les profils de température sont influencés à la fois par les transferts thermiques par convection dans les canaux et dans les zones de distribution et de collecte de l'écoulement et également par les transferts par conduction aux travers des parois métalliques situées entre les canaux et à la périphérie de la zone micro-structurée, en particulier pour les faibles débits liquides. À cause de ces transferts de chaleur parasites, la fraction du flux thermique qui est réellement transférée au travers des micro-canaux varie entre 75 et 85 % du flux thermique total en écoulement contre-courant et entre 35 et 70 % en écoulement co-courant. Les résultats des simulations numériques sont en bon accord avec les profils de température mesurés au sein du micro-échangeur. Abstract-CFD Simulation of Hydrodynamic and Thermal Performance of a Micro Heat Exchanger-To evaluate the performances and limitations of compact heat exchanger with micro-structured plates, CFD simulations of hydrodynamics and thermal transfers have been performed inside a commercial micro heat exchanger from IMM operated in liquid/liquid flows. The hydrodynamic results show that the flow rate distribution over the plates is rather homogeneous with some velocity gradient at the channel inlet due to inertial effect in the distributor. Fluid temperature profiles are both influenced by convective transfer in the channels and in the distributing/collecting sections and by conductive transfer through the metal wall at the plate periphery especially at low flow rates. Due to undesired heat transfer by conduction, the fraction of heat power really transferred inside the channels varies from 75 to 85% in counter current flow configuration and between 35 and 70% in co-current flow configuration. Computational results are successfully compared to 2D experimental temperature profiles measured inside the heat exchanger.
For the mixing and distribution of a liquid phase (12) and a gas phase (11) within a vertical rea... more For the mixing and distribution of a liquid phase (12) and a gas phase (11) within a vertical reactor (10), upstream of a granular bed, a horizontal plate (20) covers all the reactor to carry a number of vertical chimneys (40) with lateral openings (42) to take in the liquid and gas phases. Their upper ends (43) and lower ends (21) are linked to reactor zones above and below the plate. A vertical wall (30) is between the assembly of chimneys and the reactor wall to form a ring zone (28) to take at least an external feed of the liquid phase, with a lower gap (32) forming flow passages to the center section of the plate.
Opérations unitaires. Génie de la réaction chimique
On propose une etude theorique et experimentale d'un procede de debitmetrie triphasique eau-h... more On propose une etude theorique et experimentale d'un procede de debitmetrie triphasique eau-huile-gaz. Le procede retenu repose sur l'utilisation conjointe d'un melangeur, d'un venturi et de methodes ultrasonores. La validation experimentale de ce procede a mis en jeu le dimensionnement, la conception et la mise au point d'un dispositif entierement instrumente pour les ecoulements triphasiques eau-huile-air. Un modele original d'ecoulement triphasique disperse a ete etabli. Une fois valide sur la base de resultats en ecoulement eau-air, eau-huile et eau-huile-air, ce modele a permis de resoudre les problemes de metrologie lies a l'utilisation du venturi en presence de ces ecoulements. Sur la base d'une analyse critique des techniques utilisables, la mesure de la vitesse de propagation ultrasonore a ete selectionnee pour determiner la composition des ecoulements liquide-liquide. Deux modeles originaux ont ete developpes pour decrire la propagation ultr...
CFD is used to study liquid spreading in gas-liquid co-current trickle-bed reactors using two-flu... more CFD is used to study liquid spreading in gas-liquid co-current trickle-bed reactors using two-fluid approach. In order to propose a model that describes exhaustively all interaction forces acting on each fluid phase as well as dispersion mechanisms, a discussion of closure laws available in literature is proposed. Liquid dispersion is recognized to result from two main mechanisms: capillary and mechanical. The proposed model is then implemented in two trickle-bed configurations matching with two experimental set ups (Boyer et al., 2005 and Marcandelli et al., 2000). In the first configuration, simulations on a 2D axisymmetric geometry are considered and the model is validated upon a new set of experimental data. Liquid distribution obtained from gamma−ray tomography is provided for different geometrical and operating conditions. In the second configuration, a 3D simulation is considered and the model is validated upon experimental liquid flux patterns at the bed outlet. A sensitivit...
Chemie Ingenieur Technik, 2001
Chemical Engineering Science, 2002
In the petrochemical industry area, many processes are carried out using ÿxed bed reactors with c... more In the petrochemical industry area, many processes are carried out using ÿxed bed reactors with cocurrent upward or downward gas=liquid ows. One of the main problems to overcome during the scale-up of such reactors is to optimize the gas=liquid ow distribution across the reactor catalytic bed section. To accurately characterize the gas=liquid ow distribution inside a real catalytic bed, a new computed gamma-ray tomographic system has been developed to investigate two-phase ow through cold mock-ups of large scale (60 cm in diameter). In the case of developing a new reactor technology for processes working with ÿxed bed in the trickling ow regime, this type of measurement is quite important. This system, unique for such a large size catalyst bed, includes a series of 32 BGO detectors and a Cs 137 source. The performances of this experimental system have been fully evaluated through a validation including reconstruction of physical phantoms in static conditions. Several tests have been performed to measure the gas=liquid ow distribution in the catalyst bed for di erent inlet distributor conÿgurations. It is shown, in the experiments performed for the trickle ow regime, that the instrumental technique has a very good sensitivity to liquid retention measurement. When the liquid retention measurements are compared with a hydrodynamic model based on Kozeny-Carman formalism a quantitative agreement is observed.
International Journal of Multiphase Flow, 1997
be easily determined using Newtonian fluids alone. It is shown that the Debex on-line viscometer ... more be easily determined using Newtonian fluids alone. It is shown that the Debex on-line viscometer gives flow curves very similar to a conventional laboratory viscometer when this procedure is applied.
HAL (Le Centre pour la Communication Scientifique Directe), May 30, 2010
Multiphase reactors operated in fixed bed configuration are widely used in petrochemical industry... more Multiphase reactors operated in fixed bed configuration are widely used in petrochemical industry but their hydrodynamic is still not well understood. In a previous paper (Bordas et al, 2006), a new one-dimensional model able to predict the pressure drop and the mean void fraction for bubbly flows in packed beds was proposed. The equations required closure laws accounting for the liquid-solid and the gas-liquid interactions. Compared to previous models, these laws had been completely revisited, in order to better account for the flow dynamics at the pore scale. In particular, it had been demonstrated that (i) in dilute conditions, the bubble size remains of the order of the pore (ii) and that the mean bubble dynamics is somewhat similar to that of a slug, with a relative velocity at meso-scale linearly increasing with the liquid superficial velocity. Besides, that relative velocity monotonically increases with the gas flow rate ratio, a behaviour that is tentatively attributed to the formation of preferential paths for the gas phase. (iii) Based on the motion of a bubble train in capillary tubes, the two-phase flow pressure drop f ls scaled by its single-phase flow counterpart f lsφ at the same superficial liquid velocity is predicted to linearly increase with the void fraction, with a prefactor λ evolving with the Capillary number: Ψ = f ls / f lsφ =1+λ(Ca)α. Considering the capillary pressure contribution to the pressure drop, one expects λ∼Ca-1/3 [Bretherton 1961]. These proposals were only partly validated and required further confirmation. Thus, new experiments have been performed at LEGI and at IFP in order to cover an enlarged range of flow conditions while gathering all the necessary information to test the model. Attention has been paid to the measuring techniques, both to understand the exact meaning of the measured quantities and to control the uncertainty. So far, the results confirm the postulated dynamic. The model presented assumes that all the bubbles contributing to the void fraction are mobile while in some circumstances, bubbles can be trapped within the bed. Fixed bubbles can also contribute to the pressure drop, and the closure proposed does not take such contributions into account, This question was addressed by way of a thorough data analysis. Data gathered on the void fraction and pressure loss shows that the proposed closures laws for the gas dynamic and two-phase flow pressure drop are still relevant for moderate pressure conditions (up to 10 bars) and gas volumetric ratio β ranging from 20% to 70%. In the range of operating conditions considered (capillary number, gas ratio β), bubbles-bubbles interactions probably limit such blockage. Those interactions would explain also why the size distribution remains controlled by the pore characteristic dimension, through a process of continuous coalescence/breakup. Using these closures, the model sensitivity was studied and its ability to predict the void fraction and pressure loss addressed.
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2010
Simulation numérique par CFD de l'hydrodynamique et des performances thermiques d'un micro échang... more Simulation numérique par CFD de l'hydrodynamique et des performances thermiques d'un micro échangeur de chaleur-Pour évaluer les performances et les limitations d'un échangeur thermique compact composé de plaques micro-structurées, des simulations CFD de l'hydrodynamique et des transferts thermiques ont été effectués en écoulement liquide/liquide pour un micro-échangeur commercialisé par l'IMM. Les résultats de la simulation hydrodynamique montrent que la distribution des flux de l'écoulement liquide est plutôt homogène avec quelques gradients de vitesses à l'entrée des canaux à cause d'effets inertiels dans le distributeur. Les profils de température sont influencés à la fois par les transferts thermiques par convection dans les canaux et dans les zones de distribution et de collecte de l'écoulement et également par les transferts par conduction aux travers des parois métalliques situées entre les canaux et à la périphérie de la zone micro-structurée, en particulier pour les faibles débits liquides. À cause de ces transferts de chaleur parasites, la fraction du flux thermique qui est réellement transférée au travers des micro-canaux varie entre 75 et 85 % du flux thermique total en écoulement contre-courant et entre 35 et 70 % en écoulement co-courant. Les résultats des simulations numériques sont en bon accord avec les profils de température mesurés au sein du micro-échangeur. Abstract-CFD Simulation of Hydrodynamic and Thermal Performance of a Micro Heat Exchanger-To evaluate the performances and limitations of compact heat exchanger with micro-structured plates, CFD simulations of hydrodynamics and thermal transfers have been performed inside a commercial micro heat exchanger from IMM operated in liquid/liquid flows. The hydrodynamic results show that the flow rate distribution over the plates is rather homogeneous with some velocity gradient at the channel inlet due to inertial effect in the distributor. Fluid temperature profiles are both influenced by convective transfer in the channels and in the distributing/collecting sections and by conductive transfer through the metal wall at the plate periphery especially at low flow rates. Due to undesired heat transfer by conduction, the fraction of heat power really transferred inside the channels varies from 75 to 85% in counter current flow configuration and between 35 and 70% in co-current flow configuration. Computational results are successfully compared to 2D experimental temperature profiles measured inside the heat exchanger.
For the mixing and distribution of a liquid phase (12) and a gas phase (11) within a vertical rea... more For the mixing and distribution of a liquid phase (12) and a gas phase (11) within a vertical reactor (10), upstream of a granular bed, a horizontal plate (20) covers all the reactor to carry a number of vertical chimneys (40) with lateral openings (42) to take in the liquid and gas phases. Their upper ends (43) and lower ends (21) are linked to reactor zones above and below the plate. A vertical wall (30) is between the assembly of chimneys and the reactor wall to form a ring zone (28) to take at least an external feed of the liquid phase, with a lower gap (32) forming flow passages to the center section of the plate.