Thermal Dissociation of CH4 Using a Particle-Flow Chemical Reactor Exposed to Concentrated Solar Radiation

2008 ◽  
Author(s):  
Gilles Maag ◽  
Francisco Javier Gutierrez ◽  
Wojciech Lipinski ◽  
Aldo Steinfeld
Keyword(s):  
Solar Radiation ◽  
Volume Fraction ◽  
Solid Phase ◽  
Particle Volume Fraction ◽  
Thermal Dissociation ◽  
Chemical Reactor ◽  
Particle Flow ◽  
Carbonaceous Particles ◽  
Phase Volume Fraction ◽  
Concentrated Solar Radiation

The performance of a 5 kW particle-flow chemical reactor for the co-production of H2 and C by thermal decomposition of CH4 is investigated using concentrated solar radiation as the energy source of high-temperature process heat. The solar reactor features a directly-irradiated flow of CH4 laden with carbonaceous particles that serve the functions of radiant absorbers and nucleation sites for the heterogeneous cracking reaction. Main operational parameters are the solar power input, CH4 mass flow rate, and solid phase volume fraction. Their effect on the chemical conversion and solid products’ characteristics are examined for active carbon and carbon black laden particles. Higher particle volume fraction resulted in higher radiative absorption and enhanced kinetics.

Shock-Induced Multiphase Instability in a High Volume Fraction Finite-Thickness Particle Layer

2021 ◽  
Author(s):  
Bertrand Rollin ◽  
Frederick Ouellet ◽  
Bradford Durant ◽  
Rahul Babu Koneru ◽  
S. Balachandar
Keyword(s):  
Shock Tube ◽  
Volume Fraction ◽  
Solid Phase ◽  
Particle Volume Fraction ◽  
Finite Thickness ◽  
Spherical Particles ◽  
Shock Strength ◽  
Particle Volume ◽  
Particle Cloud ◽  
Particle Layer

Abstract We study the interaction of a planar air shock with a perturbed, monodispersed, particle curtain using point-particle simulations. In this Eulerian-Lagrangian approach, equations of motion are solved to track the position, momentum, and energy of the computational particles while the carrier fluid flow is computed in the Eulerian frame of reference. In contrast with many Shock-Driven Multiphase Instability (SDMI) studies, we investigate a configuration with an initially high particle volume fraction, which produces a strongly two-way coupled flow in the early moments following the shock-solid phase interaction. In the present study, the curtain is about 4 mm in thickness and has a peak volume fraction of about 26%. It is composed of spherical particles of d = 115μm in diameter and a density of 2500 kg.m−3, thus replicating glass particles commonly used in multiphase shock tube experiments or multiphase explosive experiments. We characterize both the evolution of the perturbed particle curtain and the gas initially trapped inside the particle curtain in our planar three-dimensional numerical shock tube. Control parameters such as the shock strength, the particle curtain perturbation wavelength and particle volume fraction peak-to-trough amplitude are varied to quantify their influence on the evolution of the particle cloud and the initially trapped gas. We also analyze the vortical motion in the flow field. Our results indicate that the shock strength is the primary contributor to the cloud particle width. Also, a classic Richtmyer-Meshkov instability mixes the gas initially trapped in the particle curtain and the surrounding gas. Finally, we observe that the particle cloud contribute to the formation of longitudinal vortices in the downstream flow.

Two-Way Coupling Effects in Dilute Gas-Particle Flows

1982 ◽  
Vol 104 (3) ◽  
pp. 304-311 ◽  
Author(s):  
M. Di Giacinto ◽  
F. Sabetta ◽  
R. Piva
Keyword(s):  
Stokes Equations ◽  
Volume Fraction ◽  
Solid Phase ◽  
Coupling Effect ◽  
Particle Volume Fraction ◽  
Stokes Number ◽  
Particle Volume ◽  
Fluid Field ◽  
Particle Flows ◽  
Energy Dissipated

A general analysis of gas-particle flows, under the hypotheses of number of particles large enough to consider the solid phase as a continuum and of volume fraction small enough to consider the suspension as dilute, is presented. The Stokes number Sk and the particle loading ratio β are shown to be the basic parameters governing the flow. Depending on the values of these two parameters, in one case the reciprocal interaction of the fluid and solid phases must be considered (two-way coupling), in the second case only the effect of the fluid field on the particle motion is relevant (one-way coupling). In the more general case of two-way coupling, the flow is governed by two sets of Navier-Stokes equations, one for each phase, which are coupled together through the particle volume fraction and the momentum interchange forces. The two systems of equations, expressed in the variables velocity, pressure, and particle volume fraction, are solved numerically by a finite difference scheme. The model has been applied to a duct with a sudden restriction, simulating a flow metering device. The coupling effect both on fluid and solid phase fields, the increase of pressure drop, and the energy dissipated in the fluid-solid interaction have been determined as functions of the governing parameters, Sk and β. The parametric study also indicates the ranges of β and Sk in which simplified formulations may be assumed.

The nonlinear dynamics of solidification of a binary melt with a quasi-equilibrium mushy region

1990 ◽  
Vol 68 (9) ◽  
pp. 790-793 ◽  
Author(s):  
Yu. A. Buyevich ◽  
L. Y. Iskakova ◽  
V. V. Mansurov
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Volume Fraction ◽  
Solid Phase ◽  
Internal Heat ◽  
Solid Particles ◽  
Mushy Region ◽  
Parameter Method ◽  
Quasi Equilibrium ◽  
Phase Volume Fraction

A mushy region (a two-phase zone) between the solid and liquid phases occurs often in the process of solidification of a binary melt. An analysis of the structure of the mushy region, which includes the liquid, solid particles, and dendrites extending from the bulk solid surface, is suggested. The processes of heat and mass transfer in the mushy region are considered on the basis of the small parameter method. The analysis leads to equations governing unsteady heat and mass transfer with internal heat, and mass sources within the mushy region, and it includes the condition for the absence of supercooling (the condition for the zone quasi-equilibrium), convection being neglected. The temperature, concentration of solute, and solid phase volume fraction are found. On the basis of this solution a new model of the process is formulated. Within the scope of this model the mushy region is replaced by a liquid–solid interface with discontinuous boundary conditions.

CFD Modeling of Gas Particle Flow Within a Solid Particle Solar Receiver

Solar Energy ◽  
2006 ◽  
Author(s):  
Huajun Chen ◽  
Yitung Chen ◽  
Hsuan-Tsung Hsieh ◽  
Nathan Siegel
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Solid Particle ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Operating Conditions ◽  
Solid Particles ◽  
Particle Flow ◽  
Cfd Modeling ◽  
Solar Receiver

A detailed three dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray tracing algorithm. Two kinds of solid particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the particle and gas velocity, temperature, particle solid volume fraction, and cavity efficiency.

A Receiver-Reactor for the Solar Thermal Dissociation of Zinc Oxide

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
L. O. Schunk ◽  
P. Haeberling ◽  
S. Wepf ◽  
D. Wuillemin ◽  
A. Meier ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Dissociation ◽  
Ceramic Matrix Composite ◽  
Chemical Reactor ◽  
Heat Fluxes ◽  
Solar Simulator ◽  
Rotating Cavity ◽  
Zno Particles ◽  
Concentrated Solar Radiation ◽  
Chemical Reactant

An improved engineering design of a solar chemical reactor for the thermal dissociation of ZnO at above 2000K is presented. It features a rotating cavity receiver lined with ZnO particles that are held by centrifugal force. With this arrangement, ZnO is directly exposed to concentrated solar radiation and serves simultaneously the functions of radiant absorber, chemical reactant, and thermal insulator. The multilayer cylindrical cavity is made of sintered ZnO tiles placed on top of a porous 80%Al2O3–20%SiO2 insulation and reinforced by a 95%Al2O3–5%Y2O3 ceramic matrix composite, providing mechanical, chemical, and thermal stability and a diffusion barrier for product gases. 3D computational fluid dynamics was employed to determine the optimal flow configuration for an aerodynamic protection of the quartz window against condensable Zn(g). Experimentation was carried out at PSI’s high-flux solar simulator with a 10kW reactor prototype subjected to mean radiative heat fluxes over the aperture exceeding 3000suns (peak 5880suns). The reactor was operated in a transient ablation mode with semicontinuous feed cycles of ZnO particles, characterized by a rate of heat transfer—predominantly by radiation—to the layer of ZnO particles undergoing endothermic dissociation that proceeded faster than the rate of heat transfer—predominantly by conduction—through the cavity walls.

Numerical Study on Effects of Drilling Mud Rheological Properties on the Transport of Drilling Cuttings

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
E. GhasemiKafrudi ◽  
S. H. Hashemabadi
Keyword(s):  
Pressure Drop ◽  
Velocity Profile ◽  
Volume Fraction ◽  
Solid Phase ◽  
Numerical Study ◽  
Drilling Mud ◽  
Phase Volume ◽  
Phase Volume Fraction ◽  
Pressure Fields ◽  
New Correlation

Inaccurate prediction of the required pressures can lead to a number of costly drilling problems. In this study, the hydrodynamics of mud-cuttings were numerically studied using the Mixture Model. To this end, an in-house code was developed to calculate the velocity and pressure fields. The mud velocity profile using of Herschel–Bulkley model and solid phase volume fraction were locally calculated; moreover, pressure drop through the annulus was taken into account. The effects of velocity, mud properties, and solid phase volume fraction on pressure drop were discussed and a new correlation was proposed for calculating friction factor based on corresponding parameters.

scholarly journals Characterization of Particle Flow in a Free-Falling Solar Particle Receiver

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
David Romano ◽  
Julius Yellowhair ◽  
Nathan Siegel ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Numerical Models ◽  
Particle Volume Fraction ◽  
Particle Flow ◽  
Particle Interactions ◽  
Particle Volume ◽  
Power Cycles ◽  
Particle Velocities ◽  
Free Falling ◽  
Measured Particle

Falling particle receivers are being evaluated as an alternative to conventional fluid-based solar receivers to enable higher temperatures and higher efficiency power cycles with direct storage for concentrating solar power (CSP) applications. This paper presents studies of the particle mass flow rate, velocity, particle-curtain opacity and density, and other characteristics of free-falling ceramic particles as a function of different discharge slot apertures. The methods to characterize the particle flow are described, and results are compared to theoretical and numerical models for unheated conditions. Results showed that the particle velocities within the first 2 m of release closely match predictions of free-falling particles without drag due to the significant amount of air entrained within the particle curtain, which reduced drag. The measured particle-curtain thickness (∼2 cm) was greater than numerical simulations, likely due to additional convective air currents or particle–particle interactions neglected in the model. The measured and predicted particle volume fraction in the curtain decreased rapidly from a theoretical value of 60% at the release point to less than 10% within 0.5 m of drop distance. Measured particle-curtain opacities (0.5–1) using a new photographic method that can capture the entire particle curtain were shown to match well with discrete measurements from a conventional lux meter.

Solidification and Melting of Gallium in the Presence of Magnetic Field: Experimental Simulation of Low Gravity Environment

2004 ◽  
Author(s):  
M. Charmchi ◽  
H. Zhang ◽  
W. Li ◽  
M. Faghri
Keyword(s):  
Magnetic Field ◽  
Phase Change ◽  
Volume Fraction ◽  
Solid Phase ◽  
Research Work ◽  
Transverse Magnetic ◽  
Experimental Simulation ◽  
Temperature History ◽  
Low Gravity ◽  
Phase Volume Fraction

Phase change in a simulated low gravity environment is the central topic of this research work. The application of a transverse magnetic field gives rise to Lorentz forces that can dampen the convective flows especially the buoyancy driven flows. The flow suppression depends on a dimensionless parameter namely the Hartmann number. This paper presents the experimental results for sidewall solidification and melting and therefore, addresses the fixed solid phase conditions. Gallium is used as phase change material (PCM) and both melting and solidification processes are investigated. The effects of an applied magnetic field on phase change rate and on the shape of the solid/melt interface are studied. The solid thickness is measured via ultrasonic techniques and the solid/melt interface is mapped using florescent light shadowgraphy through a transparent window. The presented data consist of temperature history, ultrasonic detection of the interface, florescent light shadowgraphy and solid phase volume fraction. The presence of the magnetic field had a marked effect on melting and natural convection whereas; phase change convection was noticeable in the solidification cases.

A Rotary Receiver-Reactor for the Solar Thermal Dissociation of Zinc Oxide

2007 ◽  
Author(s):  
L. O. Schunk ◽  
P. Haeberling ◽  
S. Wepf ◽  
D. Wuillemin ◽  
A. Meier ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Dissociation ◽  
Ceramic Matrix Composite ◽  
Chemical Reactor ◽  
Heat Fluxes ◽  
Solar Simulator ◽  
Rotating Cavity ◽  
Zno Particles ◽  
Concentrated Solar Radiation ◽  
Chemical Reactant

An improved engineering design of a solar chemical reactor for the thermal dissociation of ZnO at above 2000 K is presented. It features a rotating cavity-receiver lined with ZnO particles that are held by centrifugal force. With this arrangement, ZnO is directly exposed to concentrated solar radiation and serves simultaneously the functions of radiant absorber, chemical reactant, and thermal insulator. The multilayer cavity is made of sintered ZnO tiles placed on top of a porous 80%Al2O3-20%SiO2 insulation and reinforced by a 95%Al2O3-5%Y2O3 ceramic matrix composite, providing mechanical, chemical, and thermal stability and a diffusion barrier for product gases. 3D CFD was employed to determine the optimal flow configuration for an aerodynamic protection of the quartz window against condensable Zn(g). Experimentation was carried out at PSI’s high flux solar simulator with a 10 kW reactor prototype subjected to mean radiative heat fluxes over the aperture exceeding 3000 suns (peak 5880 suns). The reactor was operated in a transient ablation mode with semi-batch feed cycles of ZnO particles, characterized by a rate of heat transfer — predominantly by radiation — to the layer of ZnO particles undergoing endothermic dissociation that proceeded faster than the rate of heat transfer — predominantly by conduction — through the cavity walls.

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