scholarly journals Tomography-Based Analysis of Radiative Transfer in Reacting Packed Beds Undergoing a Solid-Gas Thermochemical Transformation

2009 ◽  
Author(s):  
Sophia Haussener ◽  
Wojciech Lipin´ski ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Effective Properties ◽  
Packed Bed ◽  
Steam Gasification ◽  
Domain Modeling ◽  
Thermochemical Transformation ◽  
Reaction Extent ◽  
Fluid Boundary ◽  
Point Correlation ◽  
Scattering Phase ◽  
Scattering Phase Function

A reacting packed bed undergoing a high-temperature thermochemical solid-gas transformation is considered. The steam-gasification of carbonaceous materials into syngas is selected as the model reaction. The exact 3D geometrical configuration of the packed bed is obtained by computer tomography, digitalized, and used in direct pore-level simulations to characterize its morphological and radiative transport properties as a function of the reaction extent. Two-point correlation functions and mathematical morphology operations are applied to calculate porosities, specific surfaces, particle size distributions, and representative elementary volumes. The collision-based Monte Carlo method is applied to determine the probability distribution of attenuation path length and direction of incidence at the solid-fluid boundary, which are linked to the extinction coefficient, scattering phase function, and albedo. These effective properties can then be incorporated in continuum domain modeling of the packed bed.

scholarly journals Tomography-Based Analysis of Radiative Transfer in Reacting Packed Beds Undergoing a Solid-Gas Thermochemical Transformation

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Sophia Haussener ◽  
Wojciech Lipiński ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Effective Properties ◽  
Packed Bed ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Thermochemical Transformation ◽  
Reaction Extent ◽  
Fluid Boundary ◽  
Point Correlation ◽  
Scattering Phase ◽  
Scattering Phase Function

A reacting packed-bed undergoing a high-temperature thermochemical solid-gas transformation is considered. The steam- and dry-gasification of carbonaceous materials to syngas is selected as the model reaction. The exact 3D digital geometrical representation of the packed-bed is obtained by computer tomography and used in direct pore-level simulations to characterize its morphological and radiative transport properties as a function of the reaction extent. Two-point correlation functions and mathematical morphology operations are applied to calculate porosities, specific surfaces, particle-size distributions, and representative elementary volumes. The collision-based Monte Carlo method is applied to determine the probability distribution of attenuation path length and direction of incidence at the solid-fluid boundary, which are linked to the extinction coefficient, scattering phase function, and scattering albedo. These effective properties can be then incorporated in continuum models of the reacting packed-bed.

scholarly journals Tomography-Based Determination of Effective Transport Properties for Reacting Porous Media

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Sophia Haussener ◽  
Iwan Jerjen ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Porous Media ◽  
Transport Properties ◽  
Strong Dependence ◽  
Convective Heat Transfer Coefficient ◽  
Packed Bed ◽  
Morphological Properties ◽  
High Resolution Computed Tomography ◽  
Thermochemical Transformation ◽  
Effective Transport ◽  
Reaction Extent

The effective heat and mass transport properties of a porous packed bed of particles undergoing a high-temperature solid–gas thermochemical transformation are determined. The exact 3D geometry of the reacting porous media is obtained by high-resolution computed tomography. Finite volume techniques are applied to solve the governing conservation equations at the pore-level scale and to determine the effective transport properties as a function of the reaction extent, namely, the convective heat transfer coefficient, permeability, Dupuit–Forchheimer coefficient, tortuosity, and residence time distributions. These exhibit strong dependence on the bed morphological properties (e.g., porosity, specific surface area, particle size) and, consequently, vary with time as the reaction progresses.

scholarly journals Tomography-Based Determination of Effective Transport Properties for Reacting Porous Media

2010 ◽  
Author(s):  
Sophia Haussener ◽  
Iwan Jerjen ◽  
Peter Wyss ◽  
Aldo Steinfeld
Keyword(s):  
Porous Media ◽  
Transport Properties ◽  
Strong Dependence ◽  
Convective Heat Transfer Coefficient ◽  
Packed Bed ◽  
Morphological Properties ◽  
Thermochemical Transformation ◽  
Effective Transport ◽  
Reaction Extent ◽  
Level Scale

The effective heat and mass transport properties of a porous packed bed of particles undergoing a high-temperature solid-gas thermochemical transformation are determined. The exact 3D geometry of the reacting porous media is obtained by high-resolution computer tomography. Finite volume techniques are applied to solve the governing conservation equations at the pore-level scale and to determine the effective transport properties as a function of the reaction extent, namely: the convective heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, tortuosity and residence time distributions. These exhibit strong dependence on the bed morphological properties (e.g. porosity, specific surface area, particle size) and, consequently, vary with time as the reaction progresses.

Experimental Investigation of a Packed-Bed Solar Reactor for the Steam-Gasification of Biomass Charcoal

2008 ◽  
Author(s):  
Nicolas Piatkowski ◽  
Christian Wieckert ◽  
Aldo Steinfeld
Keyword(s):  
Calorific Value ◽  
Packed Bed ◽  
Energy Conversion Efficiency ◽  
Steam Gasification ◽  
Solar Simulator ◽  
High Quality ◽  
Syngas Production ◽  
Solar Reactor ◽  
Graphite Plate ◽  
Concentrated Solar Energy

Gasification of coal, biomass, and other carbonaceous materials for high-quality syngas production is considered using concentrated solar energy as the source of high-temperature process heat. The solar reactor consists of two cavities separated by a SiC-coated graphite plate, with the upper one serving as the radiative absorber and the lower one containing the reacting packed bed that shrinks as the reaction progresses. A 5-kW prototype reactor with an 8 cm-depth, 14.3 cm-diameter cylindrical bed was fabricated and tested in the High-Flux Solar Simulator at PSI, subjected to solar flux concentrations up to 2300 suns. Beech charcoal was used as a model feedstock and converted into high-quality syngas (predominantly H2 and CO) with packed-bed temperatures up to 1500 K, an upgrade factor of the calorific value of 1.33, and an energy conversion efficiency of 29%. Pyrolysis was evident through the evolution of higher gaseous hydrocarbons during heating of the packed bed. The engineering design, fabrication, and testing of the solar reactor are described.

scholarly journals Assessing the Role of Particles in Radiative Heat Transfer during Oxy-Combustion of Coal and Biomass Blends

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Caitlyn Wolf
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Test Facility ◽  
Biomass Combustion ◽  
Radiative Fluxes ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Fuel Fragmentation

This study assesses the required fidelities in modeling particle radiative properties and particle size distributions (PSDs) of combusting particles in Computational Fluid Dynamics (CFD) investigations of radiative heat transfer during oxy-combustion of coal and biomass blends. Simulations of air and oxy-combustion of coal/biomass blends in a 0.5 MW combustion test facility were carried out and compared against recent measurements of incident radiative fluxes. The prediction variations to the combusting particle radiative properties, particle swelling during devolatilization, scattering phase function, biomass devolatilization models, and the resolution (diameter intervals) employed in the fuel PSD were assessed. While the wall incident radiative flux predictions compared reasonably well with the experimental measurements, accounting for the variations in the fuel, char and ash radiative properties were deemed to be important as they strongly influenced the incident radiative fluxes and the temperature predictions in these strongly radiating flames. In addition, particle swelling and the diameter intervals also influenced the incident radiative fluxes primarily by impacting the particle extinction coefficients. This study highlights the necessity for careful selection of particle radiative property, and diameter interval parameters and the need for fuel fragmentation models to adequately predict the fly ash PSD in CFD simulations of coal/biomass combustion.

A Comparison of Aphelion Cloud Belt Phase Functions Before and After the Mars Year 34 Global Dust Storm

2021 ◽  
Author(s):  
Alex Innanen ◽  
Brittney Cooper ◽  
Charissa Campbell ◽  
Scott Guzewich ◽  
Jacob Kloos ◽  
...  
Keyword(s):  
Dust Storm ◽  
Phase Function ◽  
Dust Storms ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Water Ice ◽  
Ice Cloud ◽  
Sky Survey ◽  
Scattering Phase ◽  
Scattering Phase Function

<p>1. INTRODUCTION</p><p>The Mars Science Laboratory (MSL) is located in Gale Crater (4.5°S, 137.4°E), and has been performing cloud observations for the entirety of its mission, since its landing in 2012 [eg. 1,2,3]. One such observation is the Phase Function Sky Survey (PFSS), developed by Cooper et al [3] and instituted in Mars Year (MY) 34 to determine the scattering phase function of Martian water-ice clouds. The clouds of interest form during the Aphelion Cloud Belt (ACB) season (L<sub>s</sub>=50°-150°), a period of time during which there is an increase in the formation of water-ice clouds around the Martian equator [4]. The PFSS observation was also performed during the MY 35 ACB season and the current MY 36 ACB season.</p><p>Following the MY 34 ACB season, Mars experienced a global dust storm which lasted from L<sub>s</sub>~188° to L<sub>s</sub>~250° of that Mars year [5]. Global dust storms are planet-encircling storms which occur every few Mars years and can significantly impact the atmosphere leading to increased dust aerosol sizes [6], an increase in middle atmosphere water vapour [7], and the formation of unseasonal water-ice clouds [8]. While the decrease in visibility during the global dust storm itself made cloud observation difficult, comparing the scattering phase function prior to and following the global dust storm can help to understand the long-term impacts of global dust storms on water-ice clouds.</p><p>2. METHODS</p><p>The PFSS consists of 9 cloud movies of three frames each, taken using MSL’s navigation cameras, at a variety of pointings in order to observe a large range of scattering angles. The goal of the PFSS is to characterise the scattering properties of water-ice clouds and to determine ice crystal geometry.  In each movie, clouds are identified using mean frame subtraction, and the phase function is computed using the formula derived by Cooper et al [3]. An average phase function can then be computed for the entirety of the ACB season.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.eda718c85da062913791261/sdaolpUECMynit/1202CSPE&app=m&a=0&c=67584351a5c2fde95856e0760f04bbf3&ct=x&pn=gnp.elif&d=1" alt="Figure 1 – Temporal Distribution of Phase Function Sky Survey Observations for Mars Years 34 and 35" width="800" height="681"></p><p>Figure 1 shows the temporal distributions of PFSS observations taken during MYs 34 and 35. We aim to capture both morning and afternoon observations in order to study any diurnal variability in water-ice clouds.</p><p>3. RESULTS AND DISCUSSION</p><p>There were a total of 26 PFSS observations taken in MY 35 between L<sub>s</sub>~50°-160°, evenly distributed between AM and PM observations. Typically, times further from local noon (i.e. earlier in the morning or later in the afternoon) show stronger cloud features, and run less risk of being obscured by the presence of the sun. In all movies in which clouds are detected, a phase function can be calculated, and an average phase function determined for the whole ACB season.  </p><p>Future work will look at the water-ice cloud scattering properties for the MY 36 ACB season, allowing us to get more information about the interannual variability of the ACB and to further constrain the ice crystal habit. The PFSS observations will not only assist in our understanding of the long-term atmospheric impacts of global dust storms but also add to a more complete image of time-varying water-ice cloud properties.</p>

scholarly journals Modeling of Aerosol Radiation-Relevant Parameters in the Troposphere of Siberia on the Basis of Empirical Data

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 414 ◽  
Author(s):  
Mikhail Panchenko ◽  
Svetlana Terpugova ◽  
Victor Pol’kin ◽  
Valerii Kozlov ◽  
Dmitry Chernov
Keyword(s):  
Complex Refractive Index ◽  
West Siberia ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Optical Characteristics ◽  
Asymmetry Factor ◽  
Size Spectrum ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Modal Radius

The paper presents the generalized empirical model of the aerosol optical characteristics in the lower 5-km layer of the atmosphere of West Siberia. The model is based on the data of long-term airborne sensing of the vertical profiles of the angular scattering coefficient, aerosol disperse composition, as well as the content of absorbing particles. The model provides for retrieval of the aerosol optical characteristics in visible and near IR wavelength ranges (complex refractive index, scattering and absorption coefficients, optical depth, single scattering albedo, and asymmetry factor of the scattering phase function). The main attention in the presented version of the model is given to two aspects: The study of the effect of the size spectrum of the absorbing substance in the composition of aerosol particles on radiative-relevant parameters (the single scattering albedo (SSA) and the asymmetry factor (AF)) and the consideration of different algorithms for taking into account the relative humidity of air. The ranges of uncertainty of SSA and AF at variations in the modal radius of the absorbing fraction at different altitudes in the troposphere are estimated.

Sign in / Sign up

Export Citation Format

Share Document