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.

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.

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.

Reduced Models for Radiative Heat Transfer Analysis Through Anisotropic Fibrous Medium

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Hervé Thierry Tagne Kamdem ◽  
Dominique Doermann Baillis
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Phase Function ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Reduced Models ◽  
Fibrous Medium ◽  
Scattering Phase ◽  
Scattering Phase Function

Reduced models for radiative heat transfer analysis through anisotropic medium are presented and evaluated. The models include two equivalent heat transfer models through isotropic medium using isotropic or Henyey–Greenstein scattering phase functions with arithmetic or weighted means radiative properties calculated over all incident direction and an anisotropic model with directional radiative properties coupled to an isotropic scattering phase function or directional anisotropically scattering phase function. The pertinence of the models is investigated by solving coupled conduction/radiation heat transfer through a slab of anisotropic fibrous medium with fiber randomly oriented in the plan parallel to the boundaries. Good agreements on heat fluxes and thermal conductivity are obtained for reduced anisotropic models and for reduced equivalent isotropic models with weighted mean radiative properties.

scholarly journals Microwave Brightness of Polar Firn as Measured by Nimbus 5 and 6 ESMR

1980 ◽  
Vol 25 (91) ◽  
pp. 85-92 ◽  
Author(s):  
A. T. C. Chang ◽  
B. J. Choudhury ◽  
P. Gloersen
Keyword(s):  
Temperature Profile ◽  
Radiative Transfer Equation ◽  
Mie Scattering ◽  
Index Of Refraction ◽  
Microwave Emission ◽  
Profile Data ◽  
Surface Polarization ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Method Of Invariant Imbedding

AbstractThe microwave emission from a half-space medium characterized by coordinate dependent scattering and absorbing centers has been calculated by numerically solving the radiative transfer equation by the method of invariant imbedding. A Mie scattering phase function and surface polarization have been included in the calculation. Also included are the physical temperature profile and the temperature variation of the index of refraction for ice. Using published values of grain-size and temperature-profile data of polar firn, the brightness temperature has been calculated for the 1.55 cm and 0.8 cm wavelengths. For selected regions in Greenland and Antarctica, the results of our calculations are in reasonable agreement with the observed Nimbus-5 and Nimbus-6 ESMR data.

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.

A PDF/Photon Monte Carlo Method for Radiative Heat Transfer in Turbulent Flames

2005 ◽  
Author(s):  
Liangyu Wang ◽  
Daniel C. Haworth ◽  
Michael F. Modest
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Numerical Models ◽  
Dominant Role ◽  
Flame Temperature ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Pollutant Emissions

Thermal radiation plays a dominant role in heat transfer for most combustion systems. Accurate predictions of radiative heat transfer are essential for the correct determination of flame temperature, flame structure, and pollutant emissions in combustion simulations. In turbulent flames, transported probability density function (PDF) methods provide a reliable treatment of nonlinear processes such as chemical reactions and radiative emission. Here a second statistical approach, a photon Monte Carlo (PMC) method, is employed to solve the radiative transfer equation (RTE). And a state-of-the-art model for spectral radiative properties, the full-spectrum k-distribution (FSK) method, is employed. The FSK method provides an efficient and accurate approach for spectral integration in radiation calculations. The resulting model is applied to simulate radiation and turbulence/radiation interactions in nonluminous turbulent non-premixed jet flames. The initial results reported here emphasize sensitivities of computed results to variations in the physical and numerical models. Results with versus without radiation, results obtained using two different RTE solvers, and results with a gray-gas approximation versus a spectral FSK method are compared.

scholarly journals Microwave Brightness of Polar Firn as Measured by Nimbus 5 and 6 ESMR

1980 ◽  
Vol 25 (91) ◽  
pp. 85-92 ◽  
Author(s):  
A. T. C. Chang ◽  
B. J. Choudhury ◽  
P. Gloersen
Keyword(s):  
Temperature Profile ◽  
Radiative Transfer Equation ◽  
Mie Scattering ◽  
Index Of Refraction ◽  
Microwave Emission ◽  
Profile Data ◽  
Surface Polarization ◽  
Scattering Phase ◽  
Scattering Phase Function ◽  
Method Of Invariant Imbedding

AbstractThe microwave emission from a half-space medium characterized by coordinate dependent scattering and absorbing centers has been calculated by numerically solving the radiative transfer equation by the method of invariant imbedding. A Mie scattering phase function and surface polarization have been included in the calculation. Also included are the physical temperature profile and the temperature variation of the index of refraction for ice. Using published values of grain-size and temperature-profile data of polar firn, the brightness temperature has been calculated for the 1.55 cm and 0.8 cm wavelengths. For selected regions in Greenland and Antarctica, the results of our calculations are in reasonable agreement with the observed Nimbus-5 and Nimbus-6 ESMR data.

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.

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