The Experts below are selected from a list of 3111 Experts worldwide ranked by ideXlab platform
Daniel J Holland - One of the best experts on this subject based on the ideXlab platform.
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investigation of void fraction schemes for use with cfd dem simulations of fluidized beds
Industrial & Engineering Chemistry Research, 2018Co-Authors: Daniel Clarke, A J Sederman, L F Gladden, Daniel J HollandAbstract:This paper investigates the spatial resolution of computational fluid dynamics–discrete element method (CFD-DEM) simulations of a bubbling fluidized bed for seven different void fraction schemes. Fluid grids with cell sizes of 3.5, 1.6, and 1.3 particle diameters were compared. The particle velocity maps from all of the void fraction schemes were in good qualitative agreement with the experimental data collected using magnetic resonance imaging (MRI). Refining the fluid grid improved the quantitative agreement due to a more accurate representation of flow near the Gas Distributor. The approach proposed by Khawaja et al. [J. Comput. Multiphase Flows 2012, 4, 183−192] provided the closest match to the exact void fraction though only the particle centered method differed significantly. These results indicate that the fluid grid used for CFD-DEM simulations must be sufficiently fine to represent the inlet flow realistically and that a void fraction scheme such as that proposed by Khawaja be used.
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investigation of void fraction schemes for use with cfd dem simulations of fluidized beds
Industrial & Engineering Chemistry Research, 2018Co-Authors: Daniel Clarke, A J Sederman, L F Gladden, Daniel J HollandAbstract:This paper investigates the spatial resolution of computational fluid dynamics–discrete element method (CFD-DEM) simulations of a bubbling fluidized bed for seven different void fraction schemes. Fluid grids with cell sizes of 3.5, 1.6, and 1.3 particle diameters were compared. The particle velocity maps from all of the void fraction schemes were in good qualitative agreement with the experimental data collected using magnetic resonance imaging (MRI). Refining the fluid grid improved the quantitative agreement due to a more accurate representation of flow near the Gas Distributor. The approach proposed by Khawaja et al. [J. Comput. Multiphase Flows 2012, 4, 183−192] provided the closest match to the exact void fraction though only the particle centered method differed significantly. These results indicate that the fluid grid used for CFD-DEM simulations must be sufficiently fine to represent the inlet flow realistically and that a void fraction scheme such as that proposed by Khawaja be used.
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Investigation of Void Fraction Schemes for Use with CFD-DEM Simulations of Fluidized Beds
2018Co-Authors: Daniel A. Clarke, L F Gladden, A J Sederman, Daniel J HollandAbstract:This paper investigates the spatial resolution of computational fluid dynamics–discrete element method (CFD-DEM) simulations of a bubbling fluidized bed for seven different void fraction schemes. Fluid grids with cell sizes of 3.5, 1.6, and 1.3 particle diameters were compared. The particle velocity maps from all of the void fraction schemes were in good qualitative agreement with the experimental data collected using magnetic resonance imaging (MRI). Refining the fluid grid improved the quantitative agreement due to a more accurate representation of flow near the Gas Distributor. The approach proposed by Khawaja et al. [J. Comput. Multiphase Flows 2012, 4, 183−192] provided the closest match to the exact void fraction though only the particle centered method differed significantly. These results indicate that the fluid grid used for CFD-DEM simulations must be sufficiently fine to represent the inlet flow realistically and that a void fraction scheme such as that proposed by Khawaja be used
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investigation of a swirling flow nozzle for a fluidised bed Gas Distributor
Chemical Engineering Science, 2015Co-Authors: Samson M Aworinde, Daniel J Holland, J. F. DavidsonAbstract:Abstract This paper relates to a multi-orifice Distributor for a Gas-fluidised bed, using many upward-facing nozzles, equally spaced in a horizontal plate. Each orifice contained a removable helical coil, which made the Gas swirl as it entered the bed. For a single orifice in such a Distributor, ultra-fast magnetic resonance imaging (MRI) and pressure measurements were applied to study: (i) the formation of jets and bubbles and (ii) the orifice pressure drop. Results from MRI show that the swirling flow induced by the helix significantly improves the fluidisation quality compared to a plain nozzle without spiral. The helix gives rise to secondary flow which increases pressure drop across the nozzle, the measured values of which are predicted satisfactorily by using a friction factor correlation for helical coils.
Ci Peng - One of the best experts on this subject based on the ideXlab platform.
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investigation of a circulating turbulent fluidized bed with a fractal Gas Distributor by electrostatic immune electrical capacitance tomography
Powder Technology, 2020Co-Authors: Shengnan Wang, Xianliang Sun, Jiatong Bao, Ci Peng, Zhiyong TangAbstract:In this paper, an electrostatic-immune AC-based electrical capacitance tomography (ECT) is developed to visualize the Gas-solid flow inside the circulating turbulent fluidized bed (C-TFB) reactor. A fractal Gas Distributor based on fractal self-similarity theory is used to improve the particle distribution by re-distributing the intake Gas. Experiments are carried out on a cold model of lab-scale C-TFB to investigate the effect of the fractal Gas Distributor using the electrostatic-immune ECT. Experimental results show that the particle concentrations with the fractal Gas Distributor are higher than those without the fractal Gas Distributor under identical operation conditions, indicating that the fractal Gas Distributor is favorable to enhance the upward movement of particles inside the C-TFB reactor. Moreover, the radial particle distribution with the fractal Gas Distributor is more even at a certain area of C-TFB, indicating that the fractal Gas Distributor can improve the radial uniformity of C-TFB within its active region.
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effect of fractal Gas Distributor on the radial distribution of particles in circulating turbulent fluidized bed
Powder Technology, 2018Co-Authors: Shengnan Wang, Xianliang Sun, Ci Peng, Zhiyong Tang, Hongjiang Liu, Yuhan SunAbstract:Abstract A novel Gas Distributor fabricated with 3D printing was used in the present work to improve the radial distribution of particles in a circulating turbulent fluidized bed (CTFB). The effect of fractal Distributor on a CTFB was studied using cold model tests and numerical simulations. At constant bed height and with other operating conditions, a higher particle concentration was obtained from the two-layer Gas Distributor, while the one-layer Gas Distributor produced a more even radial distribution. Additionally, based on the Eulerian/Eulerian method, a computational fluid dynamics (CFD) model incorporating a modified Gas-solid drag model has been used to simulate the fluidized bed. Compared with a traditional drag force model, the modified model produced more accurate predictions (from a comparison of simulated and measured values) for the distribution of the Gas and solid phases.
Trung Van Nguyen - One of the best experts on this subject based on the ideXlab platform.
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a two dimensional two phase model of a pem fuel cell
Journal of The Electrochemical Society, 2006Co-Authors: Guangyu Lin, Trung Van NguyenAbstract:A two-dimensional, two-phase, steady-state, isothermal model was developed for a fuel cell region consisting of the catalyst and Gas diffusion layers bonded to a proton exchange membrane (PEM). This model extends the previously published one-dimensional model of the Gas diffusion and catalyst layers to two dimensions in order to account for the effects of the shoulder of the Gas Distributor and the electronic conductivity of the solid phase. The new model was validated with experimental results and then used to investigate the effect of the relative dimensions of the shoulders and channels on the cell performance. The effects of the in-plane liquid water permeability and electronic conductivity of the Gas diffusion layer on cell performance were also examined. It was found that more channels, smaller shoulder widths on the Gas Distributor, and higher in-plane water permeability of the Gas diffusion layer can enhance the transport of liquid water and oxygen, leading to better cell performance. The in-plane electronic conductivity of the Gas diffusion layer was found to have minimal effect on the cell performance. However, a highly nonuniform distribution of electronic current was formed within the Gas diffusion and catalyst layers when the in-plane electronic conductivity was low.
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two phase flow model of the cathode of pem fuel cells using interdigitated flow fields
Aiche Journal, 2000Co-Authors: Trung Van NguyenAbstract:When interdigitated Gas Distributors are used in a PEM fuel cell, fluids entering the fuel cell are forced to flow through the electrodes porous layers. This characteristic increases transport rates of the reactants and products to and from the catalyst layers and reduces the amount of liquid water entrapped in the porous electrodes thereby minimizing electrode flooding. To investigate the effects of the Gas and liquid water hydrodynamics on the performance of an air cathode of a PEM fuel cell employing an interdigitated Gas Distributor, a 2-D, two-phase, multicomponent transport model was developed. Darcy's law was used to describe the transport of the Gas phase. The transport of liquid water through the porous electrode is driven by the shear force of Gas flow and capillary force. An equation accounting for both forces was derived for the liquid phase transport in the porous Gas electrode. Higher differential pressures between inlet and outlet channels yield higher electrode performance, because the oxygen transport rates are higher and liquid water removal is more effective. The electrode thickness needs to be optimized to get optimal performance because thinner electrode may reduce Gas-flow rate and thicker electrode may increase the diffusion layer thickness. For a fixed-size electrode, more channels and shorter shoulder widths are preferred.
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multicomponent transport in porous electrodes of proton exchange membrane fuel cells using the interdigitated Gas Distributors
Journal of The Electrochemical Society, 1999Co-Authors: Trung Van NguyenAbstract:Hydrodynamics of Gases in the cathode of a proton exchange membrane fuel cell that is contacted to an interdigitated Gas Distributor are investigated using a steady‐state multicomponent transport model. The model describes the two‐dimensional flow patterns and the distributions of the Gaseous species in the porous electrode and predicts the current density generated at the electrode and membrane interface as a function of various operating conditions and design parameters. Results from the model show that, with the forced flow‐through condition created by the interdigitated Gas Distributor design, the diffusion layer is greatly reduced. However, even with a much thinner diffusion layer, diffusion still plays a significant role in the transport of oxygen to the reaction surface. The results also show that the average current density generated at an air cathode increases with higher Gas flow‐through rates, thinner electrodes, and narrower shoulder widths between the inlet and outlet channels of the interdigitated Gas Distributor. © 1999 The Electrochemical Society. All rights reserved.
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a Gas Distributor design for proton exchange membrane fuel cells
Journal of The Electrochemical Society, 1996Co-Authors: Trung Van NguyenAbstract:A nonconventional Gas distribution design has been developed to improve the mass-transport rates of the reactants from the flow channels to the inner catalyst layers of the porous electrodes and to reduce the electrode water flooding problem in the cathode of proton-exchange-membrane fuel cells. Preliminary results validate the effectiveness of the design in achieving the above goals.
Zhiyong Tang - One of the best experts on this subject based on the ideXlab platform.
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investigation of a circulating turbulent fluidized bed with a fractal Gas Distributor by electrostatic immune electrical capacitance tomography
Powder Technology, 2020Co-Authors: Shengnan Wang, Xianliang Sun, Jiatong Bao, Ci Peng, Zhiyong TangAbstract:In this paper, an electrostatic-immune AC-based electrical capacitance tomography (ECT) is developed to visualize the Gas-solid flow inside the circulating turbulent fluidized bed (C-TFB) reactor. A fractal Gas Distributor based on fractal self-similarity theory is used to improve the particle distribution by re-distributing the intake Gas. Experiments are carried out on a cold model of lab-scale C-TFB to investigate the effect of the fractal Gas Distributor using the electrostatic-immune ECT. Experimental results show that the particle concentrations with the fractal Gas Distributor are higher than those without the fractal Gas Distributor under identical operation conditions, indicating that the fractal Gas Distributor is favorable to enhance the upward movement of particles inside the C-TFB reactor. Moreover, the radial particle distribution with the fractal Gas Distributor is more even at a certain area of C-TFB, indicating that the fractal Gas Distributor can improve the radial uniformity of C-TFB within its active region.
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effect of fractal Gas Distributor on the radial distribution of particles in circulating turbulent fluidized bed
Powder Technology, 2018Co-Authors: Shengnan Wang, Xianliang Sun, Ci Peng, Zhiyong Tang, Hongjiang Liu, Yuhan SunAbstract:Abstract A novel Gas Distributor fabricated with 3D printing was used in the present work to improve the radial distribution of particles in a circulating turbulent fluidized bed (CTFB). The effect of fractal Distributor on a CTFB was studied using cold model tests and numerical simulations. At constant bed height and with other operating conditions, a higher particle concentration was obtained from the two-layer Gas Distributor, while the one-layer Gas Distributor produced a more even radial distribution. Additionally, based on the Eulerian/Eulerian method, a computational fluid dynamics (CFD) model incorporating a modified Gas-solid drag model has been used to simulate the fluidized bed. Compared with a traditional drag force model, the modified model produced more accurate predictions (from a comparison of simulated and measured values) for the distribution of the Gas and solid phases.
Annelies Vandersickel - One of the best experts on this subject based on the ideXlab platform.
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design of a mw scale thermo chemical energy storage reactor
Energy Reports, 2018Co-Authors: M Angerer, S Harzschel, Konstantin Kroper, Stephan Gleis, M. Becker, Annelies VandersickelAbstract:The reversible exothermic reaction of CaO with water is considered one of the most promising reactions for high temperature thermal energy storage. In this paper, a novel technical design of a MW-scale thermochemical energy storage reactor for this reaction is presented. The aim is to provide an easy, modular and scalable reactor, suitable for industrial scale application. The reactor concept features a bubbling fluidized bed with a continuous, guided solid flow and immersed heat exchanger tubes. To investigate the reactor design, a model is build using clustered CSTRs. The technical feasibility of the concept is proven in experimental tests, which are also used to identify key parameters of the model. Fluidization of the fine CaO/Ca(OH)2 powder was found to be challenging, but problems were overcome using mild calcination conditions and a special Gas Distributor plate. Using the model, it is found, that a thermal power of 15MWcan be expected from a reactor volume of 100m3. To study influences of different parameters on the reactor model performance, a sensitivity analysis is carried out and heat transfer between the reactor and the immersed heat exchangers is found to have by far the largest influence and the reaction system performance. Future research should therefore focus more on heat transfer.
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Design of a MW-scale thermo-chemical energy storage reactor
Elsevier, 2018Co-Authors: M Angerer, S Harzschel, Konstantin Kroper, Stephan Gleis, Annelies Vandersickel, M. Becker, Hartmut SpliethoffAbstract:The reversible exothermic reaction of CaO with water is considered one of the most promising reactions for high temperature thermal energy storage. In this paper, a novel technical design of a MW-scale thermochemical energy storage reactor for this reaction is presented. The aim is to provide an easy, modular and scalable reactor, suitable for industrial scale application. The reactor concept features a bubbling fluidized bed with a continuous, guided solid flow and immersed heat exchanger tubes. To investigate the reactor design, a model is build using clustered CSTRs. The technical feasibility of the concept is proven in experimental tests, which are also used to identify key parameters of the model. Fluidization of the fine CaO/Ca(OH)2 powder was found to be challenging, but problems were overcome using mild calcination conditions and a special Gas Distributor plate. Using the model, it is found, that a thermal power of 15 MW can be expected from a reactor volume of 100 m3. To study influences of different parameters on the reactor model performance, a sensitivity analysis is carried out and heat transfer between the reactor and the immersed heat exchangers is found to have by far the largest influence and the reaction system performance. Future research should therefore focus more on heat transfer. Keywords: Thermal energy storage, CaO/Ca(OH)2, Fluidized bed, Large scal
