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 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.

Radiative Heat Transfer Using Isotropic Scaling Approximation: Application to Fibrous Medium

2005 ◽  
Vol 127 (10) ◽  
pp. 1115-1123 ◽  
Author(s):  
Hervé Thierry Kamdem Tagne ◽  
Dominique Doermann Baillis
Keyword(s):  
Heat Transfer ◽  
Exact Solution ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Scattering Problem ◽  
Incident Radiation ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Fibrous Medium

The applicability of the isotropic scaling approximation to heat transfer analysis in fibrous medium is discussed. The isotropic scaling model allows the transformation of an anisotropic scattering problem to an isotropic one. The scaled parameters are derived for general anisotropic scattering and for radiative properties dependent of the incidence radiation. Three different isotropic scaling approaches are considered: Directional isotropic scaling, mean isotropic scaling, and P1 isotropic scaling; corresponding to isotropic scaling parameters function of incident radiation, arithmetic mean over all incident direction of radiative properties, and mean on weighted radiative properties, respectively. The discrete ordinate method is used to solve the radiative transfer equation through fibrous medium. The fibers in the medium are randomly oriented either in space or parallel to the boundaries. Numerical results presented for a pure radiation problem show good accuracy on radiative heat flux between the exact solution and solution obtained with both P1 and directional isotropic scaling while using mean isotropic scaling is unsuitable. Using isotropic scaling approximation to model radiative heat transfer is faster than the exact solution and required few quadratures to converge.

Radiative Heat Transfer Using Isotropic Scaling Approximation: Application to Fibrous Medium

2004 ◽  
Author(s):  
Herve´ T. Kamdem Tagne ◽  
Dominique Doermann Baillis
Keyword(s):  
Heat Transfer ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Scattering Problem ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Discrete Ordinate Method ◽  
Discrete Ordinate ◽  
Fibrous Medium

The applicability of the isotropic scaling approximation to heat transfer analysis in fibrous medium is discussed. The isotropic scaling model allows the transformation of an anisotropic scattering problem to an isotropic one. The scaled parameters are derived for general anisotropic scattering and for radiative properties dependent of the incidence direction such as for fibrous medium. The fibers are randomly oriented either in space or parallel to the boundaries of the medium. The radiative transfer equation is solved with the discrete ordinate method and comparisons between the exact and the isotropic scaling problems for several Gauss quadrature are studied.

Radiative Transfer in Pulsed-Laser-lnduced Plasma

1997 ◽  
Vol 119 (3) ◽  
pp. 502-508 ◽  
Author(s):  
X. Xu ◽  
K. H. Song
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Plasma Layer ◽  
Pulsed Laser ◽  
In Situ Monitoring ◽  
Radiative Properties ◽  
Heat Transfer Analysis ◽  
Laser Induced Plasma

When a high-power pulsed laser interacts with materials, a plasma layer containing micrometer-size particles is formed above the target surface. The laser induced plasma changes the energy coupling mechanism between the laser beam and the target. This work investigates the radiative heat transfer process in the excimer laser generated plasma layer on the Ni specimen, in the laser fluence range between 1.5 and 5 J/cm2. Novel diagnostic techniques are developed to measure transient transmission and scattering of the thin plasma layer within the duration of the laser pulse. Based on the measurement results, radiative heat transfer analysis is performed to evaluate the radiative properties of the plasma layer, including the optical depth, the absorption coefficient, the single scattering phase function, and the scattering size parameters. Knowledge of the radiative properties of the laser induced plasma helps to understand the energy transfer process during laser-materials interaction. Further, this work demonstrates the feasibility of using the transient scattering measurement for in situ monitoring of the size of the laser ejected particles.

scholarly journals Radiative Heat Transfer Analysis in a Marine Boiler Furnace

1986 ◽  
Vol 21 (5) ◽  
pp. 311-316
Author(s):  
Hiroshi Hayasaka ◽  
Kazuhiko Kudo ◽  
Hiroshi Taniguchi ◽  
Noboru Okigami ◽  
Taketoshi Takahashi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Heat Transfer Analysis ◽  
Boiler Furnace ◽  
Marine Boiler

Spectral Radiative Heat Transfer Analysis of the Planar SOFC

2004 ◽  
Author(s):  
David L. Damm ◽  
Andrei G. Fedorov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fuel Cells ◽  
Solid Oxide Fuel Cells ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Solid Oxide ◽  
Radiative Properties ◽  
Radiative Heat Flux ◽  
Oxide Fuel

Thermo-mechanical failure of components in planar-type solid oxide fuel cells (SOFCs) depends strongly on the local temperature gradients at the interfaces of different materials. Therefore, it is of paramount importance to accurately predict the temperature fields within the stack, especially near the interfaces. Because of elevated operating temperatures (of the order of 1000 K or even higher), radiation heat transfer could become a dominant mode of heat transfer in the SOFCs. In this study, we extend our recent work on radiative effects in solid oxide fuel cells (Journal of Power Sources, Vol. 124, No. 2, pp. 453–458) by accounting for the spectral dependence of the radiative properties of the electrolyte material. The measurements of spectral radiative properties of the polycrystalline yttria-stabilized zirconia (YSZ) electrolyte we performed indicate that an optically thin approximation can be used for treatment of radiative heat transfer. To this end, the Schuster-Schwartzchild two-flux approximation is used to solve the radiative transfer equation (RTE) for the spectral radiative heat flux, which is then integrated over the entire spectrum using an N-band approximation to obtain the total heat flux due to thermal radiation. The divergence of the total radiative heat flux is then incorporated as a heat sink into a 3-D thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT CFD software. The results of sample calculations are reported and compared against the baseline cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.

Impact of Soot Radiative Properties, Pressure and Soot Volume Fraction on Radiative Heat Transfer in Turbulent Sooty Flames

2020 ◽  
Author(s):  
Kevin Torres Monclard ◽  
Olivier Gicquel ◽  
Ronan Vicquelin
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Jet Flame ◽  
Soot Particles

Abstract The effect of soot radiation modeling, pressure, and level of soot volume fraction are investigated in two ethylene-air turbulent flames: a jet flame at atmospheric pressure studied at Sandia, and a confined pressurized flame studied at DLR. Both cases have previously been computed with large-eddy simulations coupled with thermal radiation. The present study aims at determining and analyzing the thermal radiation field for different models from these numerical results. A Monte-Carlo solver based on the Emission Reciprocity Method is used to solve the radiative transfer equation with detailed gas and soot properties in both configurations. The participating gases properties are described by an accurate narrowband ck model. Emission, absorption, and scattering from soot particles are accounted for. Two formulations of the soot refractive index are considered: a constant value and a wavelength formulation dependency. This is combined with different models for soot radiative properties: gray, Rayleigh theory, Rayleigh-Debye-Gans theory for fractal aggregates. The effects of soot radiative scattering is often neglected since their contribution is expected to be small. This contribution is determined quantitatively in different scenarios, showing great sensitivity to the soot particles morphology. For the same soot volume fraction, scattering from larger aggregates is found to modify the radiative heat transfer noticeably. Such a finding outlines the need for detailed information on soot particles. Finally, the role of soot volume fraction and pressure on radiative interactions between both solid and gaseous phases is investigated.

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