scholarly journals Modeling of Ceria Reduction in a Solar Thermochemical Reactor via DEM Method

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Han Zhang ◽  
Joseph D. Smith ◽  
Keyword(s):  
Gas Flow ◽  
Three Dimensional ◽  
Textural Properties ◽  
Power Input ◽  
Reduction Reaction ◽  
Wide Range ◽  
Radiative Power ◽  
Solar Thermochemical ◽  
Ceria Reduction ◽  
Ceo2 Reduction

Solar thermochemical reactor provides an attractive approach that utilizes the most common solar radiation as the thermal driving force to motivate the reaction between CO2 and metal oxides, which is also called metal oxide redox pair-based thermochemical cycles. The CeO2/CeO2-δ is widely used in the two-step redox process due to its advantages including fast-redox kinetics, high crystallographic stability of a wide range of reacting oxygen non-stoichiometry, and relatively high oxygen solid-state conductivity. In this work, a three-dimensional transient numerical analysis has been completed to study the performance of a CeO2 reduction reaction in a 1/8th segment region of a novel partition cavity-receiver reactor. The porous CeO2 catalyst was analyzed using the discrete element method (DEM) to capture the heat transfer and reactive performances. The catalyst textural properties (particle size and void fraction) and reaction conditions (gas flow rate and radiative power input) were investigated in the CeO2 reduction reaction. The results indicated that increasing the catalyst specific surface area and the temperature are beneficial to the O2 production and further CO2 conversion.

scholarly journals High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis

2021 ◽  
Author(s):  
Meng Ge ◽  
Yanzhi Wang ◽  
Francesco Carraro ◽  
Weibin Liang ◽  
Morteza Roostaeinia ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
High Throughput ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Reduction Reaction ◽  
New Materials ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
Wide Range ◽  
Metal Organic

<p>Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1<a>, </a>was first discovered in a trace amount during the study of a known ZIF-CO<sub>3</sub>-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm<sup>-</sup>). With a composition of Zn<sub>3</sub>(mIm)<sub>5</sub>(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalysis for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications. </p>

Numerical Simulation of Heat Transfer in a 3D Cavity-Receiver

2015 ◽  
Author(s):  
Parthasarathy Pandi ◽  
Patrick Le Clercq
Keyword(s):  
Material Properties ◽  
Measurement Data ◽  
Power Input ◽  
Momentum Equation ◽  
Process Models ◽  
Conductive Heat ◽  
Recirculating Flow ◽  
Radiative Power ◽  
Ceria Reduction ◽  
Energy Equations

The unsteady 3D fluid flow coupled to radiative, convective, and conductive heat transfers are computed within a cavity-receiver that was successfully tested experimentally. A Monte-Carlo radiation model is used in the fluid regions of the reactor with source terms outside the cavity’s window to account for the concentrated radiative power input. Darcy’s law for the viscous regime and the Forchheimer’s term for the inertial regime are used in the momentum equation to account for the pressure drop within the porous region (RPC). Two separate energy equations for the solid and for the fluid regions of the porous domain are solved in order to capture the non-equilibrium effects in that region. Rosseland diffusion approximation is used in the solid regions of the RPC domain. The material properties and boundary conditions were taken from published experimental measurements. The simulation results are compared to the measurement data collected during the pre-heating and the ceria reduction phases, which sum up to four different radiative power inputs. Results of the comparison are very good and constitute the verification that the numerical methods, physical sub-process models and material properties are adequately selected and implemented. An analysis regarding the heat balance, the recirculating flow and, the effect of dual-scale porosity is also presented.

scholarly journals Three-dimensional temperature and velocity measurements in fluids using thermographic phosphor tracer particles

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Moritz Stelter ◽  
Fabio J. W. A. Martins ◽  
Frank Beyrau ◽  
Benoît Fond
Keyword(s):  
Gas Flow ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Fluid Temperature ◽  
Velocity Measurements ◽  
Tomographic Piv ◽  
Tracer Particles ◽  
Thermographic Phosphor ◽  
Wide Range ◽  
Ratio Imaging

Many flows of technical and scientific interest are intrinsically three-dimensional. Extracting slices using planar measurement techniques allows only a limited view into the flow physics and can introduce ambiguities while investigating the extent of 3D regions. Nowadays, thanks to tremendous progress in the field of volumetric velocimetry, full 3D-3C velocity information can be gathered using tomographic PIV or PTV hence eliminating many of these ambiguities (Discetti and Coletti, 2018; Westerweel et al., 2013). However, for scalar quantities like temperature, 3D measurements remain challenging. Previous approaches for coupled 3D thermometry and velocimetry combined astigmatism PTV with encapsulated europium chelates particles (Massing et al., 2018) or tomographic PIV with thermochromic liquid crystals particles (Schiepel et al., 2021). Here we present a new technique based on solid thermographic phosphor tracer particles, which have been extensively used for planar fluid temperature and velocity measurements (Abram et al., 2018) and are applicable in a wide range of temperatures. The particles are seeded into a gas flow where their 3D positions are retrieved by triangulation from multiple views and their temperatures are derived from two-colour luminescence ratio imaging. In the following, the experimental setup and key processing steps are described before a demonstration of the concept in a turbulent heated jet is shown.

scholarly journals High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis

2021 ◽  
Author(s):  
Meng Ge ◽  
Yanzhi Wang ◽  
Francesco Carraro ◽  
Weibin Liang ◽  
Morteza Roostaeinia ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
High Throughput ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Reduction Reaction ◽  
New Materials ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
Wide Range ◽  
Metal Organic

<p>Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1<a>, </a>was first discovered in a trace amount during the study of a known ZIF-CO<sub>3</sub>-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm<sup>-</sup>). With a composition of Zn<sub>3</sub>(mIm)<sub>5</sub>(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalysis for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications. </p>

scholarly journals High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis

2021 ◽  
Author(s):  
Meng Ge ◽  
Yanzhi Wang ◽  
Francesco Carraro ◽  
Weibin Liang ◽  
Morteza Roostaeinia ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
High Throughput ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Reduction Reaction ◽  
New Materials ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
Wide Range ◽  
Metal Organic

<p>Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1<a>, </a>was first discovered in a trace amount during the study of a known ZIF-CO<sub>3</sub>-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm<sup>-</sup>). With a composition of Zn<sub>3</sub>(mIm)<sub>5</sub>(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalysis for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications. </p>

scholarly journals Influences of protoplanet-induced three-dimensional gas flow on pebble accretion

2020 ◽  
Vol 633 ◽  
pp. A81 ◽  
Author(s):  
Ayumu Kuwahara ◽  
Hiroyuki Kurokawa
Keyword(s):  
Shear Flow ◽  
Gas Flow ◽  
Gravitational Interaction ◽  
Three Dimensional ◽  
Stokes Number ◽  
Thermal Mass ◽  
Hydrodynamical Simulation ◽  
Wide Range ◽  
Accretion Model ◽  
Hydrodynamical Simulations

Context. The pebble accretion model has the potential to explain the formation of various types of planets. The main difference between this and the planetesimal accretion model is that pebbles not only experience the gravitational interaction with the growing planet but also a gas drag force from the surrounding protoplanetary disk gas. Aims. A growing planet embedded in a disk induces three-dimensional (3D) gas flow, which may influence pebble accretion. However, so far the conventional pebble accretion model has only been discussed in the unperturbed (sub-)Keplerian shear flow. In this study, we investigate the influence of 3D planet-induced gas flow on pebble accretion. Methods. Assuming a nonisothermal, inviscid gas disk, we perform 3D hydrodynamical simulations on the spherical polar grid, which has a planet located at its center. We then numerically integrate the equation of motion of pebbles in 3D using hydrodynamical simulation data. Results. We find that the trajectories of pebbles in the planet-induced gas flow differ significantly from those in the unperturbed shear flow for a wide range of investigated pebble sizes (St = 10−3–100, where St is the Stokes number). The horseshoe flow and outflow of the gas alter the motion of the pebbles, which leads to a reduction of the width of the accretion window, wacc, and the accretion cross section, Aacc. On the other hand, the changes in trajectories also cause an increase in the relative velocity of pebbles to the planet, which offsets the reduction of wacc and Aacc. As a consequence, in the Stokes regime, the accretion probability of pebbles, Pacc, in the planet-induced gas flow is comparable to that in the unperturbed shear flow except when the Stokes number is small, St ~ 10−3, in 2D accretion, or when the thermal mass of the planet is small, m = 0.03, in 3D accretion. In contrast, in the Epstein regime, Pacc in the planet-induced gas flow becomes smaller than that in the shear flow in the Stokes regime in both 2D and 3D accretion, regardless of assumed St and m. Conclusions. Our results combined with the spacial variety of turbulence strength and pebble size in a disk, suggest that the 3D planet-induced gas flow may be helpful to explain the distribution of exoplanets and the architecture of the Solar System.

Multiphase Particle-in-Cell Simulations of Flow in a Gas-Solid Riser

Volume 1 ◽  
2004 ◽  
Author(s):  
K. A. Williams ◽  
D. M. Snider ◽  
J. R. Torczynski ◽  
S. M. Trujillo ◽  
T. J. O’Hern
Keyword(s):  
Gas Flow ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Extensive Study ◽  
Computational Results ◽  
Particle In Cell ◽  
Large Numbers ◽  
Wide Range ◽  
Experimental Values

The commercial computational fluid dynamics (CFD) code Arena-flow is used to simulate the transient, three-dimensional flow in a gas-solid riser at Sandia National Laboratories. Arena-flow uses a multiphase particle-in-cell (MP-PIC) numerical method. The gas flow is treated in an Eulerian manner, and the particle flow is represented in a Lagrangian manner by large numbers of discrete particle clouds with distributions of particle properties. Simulations are performed using the experimental values of the gas superficial velocity and the solids mass flux in the riser. Fluid catalytic cracking (FCC) particles are investigated. The experimental and computed pressure and solid-volume-fraction distributions are compared and found to be in reasonable agreement although the experimental results exhibit more variation along the height of the riser than the computational results do. An extensive study is performed to assess the sensitivity of the computational results to a wide range of physical and numerical parameters. The computational results are seen to be robust. Thus, the uncertainties in these parameters cannot account for the differences between the experimental and computational results.

Numerical Investigation of the Effect of Micro Channel Bends Angle

2016 ◽  
Author(s):  
Olga Rovenskaya ◽  
Giulio Croce
Keyword(s):  
Mass Flow ◽  
Gas Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Obtuse Angle ◽  
Bend Angle ◽  
Micro Channel ◽  
Channel Geometry ◽  
Wide Range

A pressure driven compressible gas flow through three-dimensional microchannel with bend of various angles is investigated using Navier–Stokes equations coupled with the first-order Maxwell slip boundary condition along with Smoluchowski temperature jump definition. A wide range of bend angles from 60° to 180° is considered. The details of the flow structures near the corner are analyzed, investigating the competing effects of rarefaction, compressibility and geometry on the channel performances. The bent results are compared to those from the equivalent straight micro-channel geometry in terms of mass flow rate and Poiseuille number. The analysis of the flow structure shows that the channel geometry is important in microfluidic applications. In particular, it is found that a micro-channel with bend angle less than 90 degrees produces an increase in mass flow with respect to the straight one, while obtuse angle bends produce a mass flux reduction. For the sharp angle the flow separation and recirculation occur in the corner of the bend and this becomes more critical as the bend angle decreases. The rarefaction alleviates the geometry effect, while compressibility enhances it.

Experimental Investigation of Vortex Flow in a Two-Chamber Solar Thermochemical Reactor

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Erik E. Koepf ◽  
Matthew D. Lindemer ◽  
Suresh G. Advani ◽  
Ajay K. Prasad
Keyword(s):  
High Temperature ◽  
Flow Visualization ◽  
Large Scale ◽  
Gas Flow ◽  
Vortex Flow ◽  
Solar Reactor ◽  
Concentrated Solar Energy ◽  
Wide Range ◽  
Reactor Geometry ◽  
Solar Thermochemical

Recent advances in the field of large-scale solar thermochemical processing have given rise to substantial research efforts and demonstration projects. Many applications of high-temperature solar-thermal technology employ an enclosed cavity environment, thus requiring a transparent window through which concentrated solar energy can enter. One configuration employed is a two-cavity reactor connected by a narrow aperture, where solar flux entering through the window is focused at the aperture plane before diverging into the lower chamber, where the chemical reaction occurs. For the Zn/ZnO thermochemical cycle where Zn is solar-thermally reduced from ZnO in a high-temperature cavity environment, effective removal of the product gas stream containing zinc vapor is of paramount importance to prevent fouling by condensation on the reactor window. Two argon-jet configurations, tangential and radial, located around the circumference of the upper chamber are used to control the gas flow within the reactor cavity. First, the tangential jets drive a vortex flow, and second, the radial wall jet travels across the window before converging at the reactor center line and turning downward to create a downward jet. The tangential jet-induced flow creates a rotating vortex, contributing to overall flow stability, and the radial jet-induced downward flow counters the updraft created by the vortex while actively cooling and sweeping clear the inner surface of the window. Flow visualization in a full-scale transparent model of the reactor using smoke and laser illumination is employed to characterize the effectiveness of aerodynamic window clearing and to characterize the processes by which a vortex flow develops and breaks down in a two-chamber solar reactor geometry. Based on a large dataset of flow visualization images, a metric is developed to define vortex stability over a wide range of flow conditions and identify an ideal operating range for which a vortex formation path is established that maintains stable flow patterns and removes product gases while minimizing the use of argon gas. The predominant influence of vortex instability and breakdown is identified and examined for the case of a beam-down, two-chamber solar reactor geometry.

scholarly journals High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis

2021 ◽  
Author(s):  
Meng Ge ◽  
Yanzhi Wang ◽  
Francesco Carraro ◽  
Weibin Liang ◽  
Morteza Roostaeinia ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
High Throughput ◽  
Metal Organic Framework ◽  
Three Dimensional ◽  
Reduction Reaction ◽  
New Materials ◽  
X Ray Diffraction ◽  
Zeolitic Imidazolate Framework ◽  
Wide Range ◽  
Metal Organic

<p>Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1<a>, </a>was first discovered in a trace amount during the study of a known ZIF-CO<sub>3</sub>-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm<sup>-</sup>). With a composition of Zn<sub>3</sub>(mIm)<sub>5</sub>(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalysis for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications. </p>

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