Modeling and analysis of 3D radiative heat transfer in combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yue Zhou ◽  
Xijuan Zhu ◽  
Qisheng Guo ◽  
Pengcheng Qi ◽  
Jing Ma
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Thermal Radiation ◽  
Numerical Method ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiant Energy ◽  
Radiative Properties ◽  
Direct Technique

Abstract Compared with wall emission, gas thermal radiation is much more complicated because of its nongray and volumetric property. In this paper, a numerical method is established to calculate 3D radiative heat transfer in combustor by modelling radiative transfer as well as nongray radiative properties of combustion gases. Energy exchanges caused by thermal radiation and conduction are calculated and compared in a rectangular combustor, which shows the significant role of thermal radiation in heating fuel-air mixtures and prompting internal combustion reactions. Besides, radiative heat flux on the wall is also quite obvious although a non-contacting flow case, revealing the special challenges for thermal protections brought by radiant energy. Lastly, increasing the working pressure means much more participating species in radiative transfer process and the radiative effects will be also magnified. The numerical method in this paper provides a direct technique to analyze the role of thermal radiation in complex thermochemical reactions while the application case proves the necessity of coupling a high-accuracy radiation model when simulating combustion and flame propagation.

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.

Sphere-to-Sphere Radiative Transfer Coefficient for Packed Sphere System

2001 ◽  
Author(s):  
S. H.-K. Lee ◽  
S. C.-H. Ip ◽  
A. K. C. Wu
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Transfer Coefficient ◽  
Radiative Heat Transfer ◽  
Transfer Equation ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Radiative Properties ◽  
Equation Approach ◽  
Packed Sphere

Abstract Rapid sintering is one of the most attractive metalworking technologies due to its ability to fabricate the final product with different microstructure in an economical manner. During this process, the high heating rate would induce a great thermal gradient to the sintering part. Such temperature differences affect the microstructure of the product, which in turn leads to the occurrence of microstructure defects. However, for this non-isothermal sintering, the present Radiative Transfer Equation approach or Units/Cells approach cannot effectively compute the temperature distributions inside the porous media, so as to predict the part defects. Cumbersome computations are needed for the Radiative Transfer Equation approach. For the Units/Cells approach, the use of regular assembly in the model limits the analysis of complex packed sphere systems. This study seeks to simplify the entire computational process for different packed sphere systems. By introducing a Radiative Transfer Coefficient (RTC) approach, the computation of radiative heat transfer within the porous bed can be enhanced. The newly introduced Radiative Transfer Coefficient is defined as the ratio of radiative energy exchange, including direct and indirect exchange, from the emitting sphere to the receiving sphere, which is a function of the system microstructure and radiative properties. A set of energy-balanced algebraic equations can then be established. With an appropriate initial energy guess for each sphere, these equations can be solved by the Gauss-Seidel iteration scheme, thereby computing the radiative heat transfer in packed sphere systems with different microstructures and radiative properties. The temperature for each sphere can therefore be computed right away. This model has been validated in different perspectives. With this RTC approach, the overall computational time required is significantly shorter, providing a set of fine-resolution temperature solution.

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 Effects of radiative heat transfer on the structure of turbulent supersonic channel flow

2011 ◽  
Vol 677 ◽  
pp. 417-444 ◽  
Author(s):  
S. GHOSH ◽  
R. FRIEDRICH ◽  
M. PFITZNER ◽  
CHR. STEMMER ◽  
B. CUENOT ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiation Effects ◽  
Radiative Heat ◽  
Pure Water ◽  
Molecular Transport ◽  
Working Fluid ◽  
Mean Flow ◽  
Total Energy Balance

The interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport.

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.

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