High-Temperature Emission Characteristics of Open-Cellular Porous Plates

2007 ◽  
Author(s):  
Bundit Krittacom ◽  
Kouichi Kamiuto
Keyword(s):  
Porous Plate ◽  
Radiative Properties ◽  
Asymmetry Factor ◽  
Emission Characteristics ◽  
Numerical Predictions ◽  
Isothermal Plane ◽  
Open Cell Foam ◽  
Alumino Silicate ◽  
Scattering Phase ◽  
Scattering Phase Function

Spectral or total normal emittances of an isothermal, plane-parallel, open-cellular porous plate placed on an opaque substrate were investigated theoretically. The equation of transfer governing the radiation field was solved using Barkstrom’s finite difference method and our improved P1 approximation. The necessary radiative properties of open-cellular porous materials such as the extinction coefficient, the albedo and the asymmetry factor of a scattering phase function were evaluated using Kamiuto’s model. Emission characteristics of three kinds of open–cell foam including Alumino-Silicate, Cordierite and Ni–Cr foams were examined. Obtained theoretical results were compared with available experimental data. A comparison between numerical predictions based on Barkstrom’s method and available spectral or total normal emittance data reported in literature shows satisfactory agreements within an experimental uncertainty. Moreover, it is found that our improved P1 approximation yields good results in predicting spectral or total normal emittances of isothermal, open-cellular porous plates.

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.

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.

Radiative Transfer in Axisymmetric, Finite Cylindrical Enclosures

1986 ◽  
Vol 108 (2) ◽  
pp. 271-276 ◽  
Author(s):  
M. P. Mengu¨c¸ ◽  
R. Viskanta
Keyword(s):  
Finite Element ◽  
Radiative Transfer ◽  
Numerical Solutions ◽  
Radiative Transfer Equation ◽  
Radiative Properties ◽  
Radiation Characteristics ◽  
Scattering Phase ◽  
Model Equations ◽  
Scattering Phase Function ◽  
Finite Element Schemes

A solution of the radiative transfer equation for an axisymmetric cylindrical enclosure containing radiatively participating gases and particles is presented. Nonhomogeneities of the radiative properties of the medium as well as of the radiation characteristics of the boundaries are allowed for, and the boundaries are assumed to be diffusely emitting and reflecting. The scattering phase function is represented by the delta-Eddington approximation to account for highly forward scattering by particulates. The model for radiative transfer is based on the P1 and P3-spherical harmonics approximations. Numerical solutions of model equations are obtained using finite-difference as well as finite-element schemes.

Effect of Configuration on the Radiative Properties of High Density Fiber Composites

2009 ◽  
Author(s):  
Siu-Chun Lee
Keyword(s):  
Phase Function ◽  
Fiber Composites ◽  
High Density ◽  
Radiative Properties ◽  
Numerical Analyses ◽  
Fiber Bundles ◽  
Scattering Coefficients ◽  
Polar Orientation ◽  
Scattering Phase ◽  
Scattering Phase Function

The influence of the geometric arrangement of fiber bundles on the radiative properties of high density woven fiber composites are examined in this paper. Of particular interest is the effect of the polar orientation of fiber bundles on the angular variation of the extinction and scattering coefficients and scattering phase function. The configuration effect is examined by numerical analyses on four types of cross-ply composites with fiber bundles at specific polar inclinations. The numerical analyses utilized the theoretical model that accounts for dependent scattering within, and uncorrelated scattering between, the dense fiber bundles. The extinction and scattering coefficients and scattering phase function are shown to depend strongly on the spatial orientation of the fiber bundles. These results indicate the feasibility of customizing the radiative properties and thus radiative transport by tailoring the geometric configuration of the fiber bundles.

Numerical Study on the Influence of Radiative Properties in Porous Media Combustion

2001 ◽  
Vol 123 (5) ◽  
pp. 951-957 ◽  
Author(s):  
Isabel Malico ◽  
Jose´ Carlos F. Pereira
Keyword(s):  
Porous Media ◽  
Numerical Study ◽  
Species Conservation ◽  
Radiative Properties ◽  
Isotropic Scattering ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Experimental Values ◽  
Phase Functions ◽  
Porous Media Combustion

The importance of radiation and of radiative properties (extinction coefficient, scattering albedo and scattering phase function) in inert porous media combustion was numerically assessed. The two-dimensional mass, momentum, solid and gas energy, and species conservation equations were solved. Emission, absorption and scattering by the porous media were taken into consideration and the S6 approximation was used to solve the radiative transfer equation. The temperature profiles are very sensitive to a perturbation in the radiative coefficients, particularly when the scattering albedo is increased. When compared to the isotropic scattering assumption, using zero, large diffuse spheres’, linear-anisotropic and modified Henyey–Greenstein phase functions leads to an average temperature difference no bigger than 7 percent. When radiation is neglected, the predicted temperature profile is not in agreement with the available experimental values.

Apparent Radiative Properties and Radiation Scattering by a Semitransparent Hemispherical Shell

2002 ◽  
Vol 124 (6) ◽  
pp. 1088-1094 ◽  
Author(s):  
Tai-Hsi Fan ◽  
Andrei G. Fedorov
Keyword(s):  
Glass Melting ◽  
Radiative Properties ◽  
Fundamental Interest ◽  
Volumetric Heating ◽  
Hemispherical Shell ◽  
Slag Foaming ◽  
Parallel Layer ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Tracing Techniques

Knowledge of the apparent radiative properties of a semitransparent hemispherical shell placed on an opaque surface is of fundamental interest and is also important to a number of applications in materials processing and manufacturing, ranging from metallurgical slag foaming to batch foams in glass melting to hollow bead fabrication. This paper extends our recent work [7]using the analytical and numerical ray tracing techniques to study radiative transfer in the system described. Specifically, the local volumetric heating rate and the scattering phase function of a thin hemispherical shell exposed to incident collimated radiation are calculated both analytically and numerically, and the results are discussed in detail. To further elucidate the results, the comparison is made of the total apparent transmittance of the hemispherical shell to a plane parallel layer of semitransparent material.

Apparent Radiative Properties and Radiation Scattering by a Semitransparent Hemispherical Shell

2001 ◽  
Author(s):  
Tai-Hsi Fan ◽  
Andrei G. Fedorov
Keyword(s):  
Glass Melting ◽  
Radiative Properties ◽  
Fundamental Interest ◽  
Volumetric Heating ◽  
Hemispherical Shell ◽  
Slag Foaming ◽  
Parallel Layer ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Tracing Techniques

Abstract Knowledge of the apparent radiative properties of the semitransparent hemispherical shell placed on an opaque surface is of the fundamental interest and also important to a number of application in materials processing and manufacturing ranging from metallurgical slag foaming to batch foams in glass melting to hollow bead fabrication. This paper extends our recent work [7] on using the analytical and numerical ray tracing techniques to study radiative transfer in the system described. Specifically, the local volumetric heating rate and the scattering phase function of a thin hemispherical shell exposed to incident collimated radiation are calculated both analytically and numerically, and the results are discussed in detail. To further elucidate the results, the comparison is made of the total apparent transmittance of the hemispherical shell to a plane parallel layer of semitransparent material.

Monte Carlo Simulation of Radiative Heat Transfer in Coarse Fibrous Media

2003 ◽  
Vol 125 (4) ◽  
pp. 748-752 ◽  
Author(s):  
Eugen Nisipeanu ◽  
Peter D. Jones
Keyword(s):  
Monte Carlo ◽  
Radiative Heat ◽  
Orientation Angle ◽  
Index Of Refraction ◽  
Radiative Properties ◽  
Fibrous Media ◽  
Polar Orientation ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Orientation Bias

Direct Geometric Monte Carlo modeling of a fibrous medium is undertaken. The medium is represented as a monodisperse array, with known solidity, of randomly oriented cylinders of known index of refraction. This technique has the advantage that further radiative properties of the medium (absorption coefficient, scattering albedo, scattering phase function) are not required, and the drawback that its’ Snell- and Fresnel-generated dynamics suggest a limitation to large, smooth fibers. It is found that radiative heat flux results are highly dependent on bias in the polar orientation angle (relative to the boundary planes) of the fibers. Randomly oriented fiber results compare well to both the large (specular radiosity method) and small (radiative transfer equation) limits, while the results of previous experiments lie within the range of simulation results generated using varying degrees of orientation bias.

A Quasidependent Scattering Radiative Properties Model for High Density Fiber Composites

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Siu-Chun Lee
Keyword(s):  
Near Field ◽  
Incident Radiation ◽  
Fiber Composites ◽  
Mie Scattering ◽  
Radiative Properties ◽  
Field Interaction ◽  
Scattering Approximation ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Spatially Oriented

This paper presents a theoretical model for the radiative properties of fiber composites fabricated of spatially oriented fiber strands that contain closely spaced fibers in the Mie scattering regime. Dependent scattering within the dense fiber strands is accounted for by utilizing the solution of Maxwell’s equations that included the near field interaction of cylindrical waves. Scattering between strands is shown to be uncorrelated due to their macroscopic dimensions compared with the wavelength of the incident radiation. The model is called quasidependent scattering approximation (QDA), as the radiative properties are formulated as the uncorrelated sum of the dependent scattering properties of the constituent fiber strands. The extinction coefficient, scattering coefficient, and scattering phase function are derived for fiber composites of arbitrary internal architecture. The application of the QDA model is demonstrated by means of numerical analyses on two types of fiber composites.

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