scholarly journals Influence of the Narrow Band Nonuniformity on the Evaluation of Heat Flux on the Furnace Wall by Radiative Heat Transfer

2005 ◽  
Vol 71 (704) ◽  
pp. 1120-1125
Author(s):  
Tatsuyuki OKAMOTO ◽  
Atsushi MORIMUNE ◽  
Toshimi TAKAGI
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Narrow Band ◽  
Furnace Wall

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.

Spectral Radiative Heat Transfer Analysis of the Planar SOFC

2005 ◽  
Vol 2 (4) ◽  
pp. 258-262 ◽  
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 1000K 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 [J. Power Sources, 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 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 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 three-dimensional thermo-fluid model of a SOFC through the user-defined function utility in the commercial FLUENT computational fluid dynamics software. The results of sample calculations are reported and compared against the base line cases when no radiation effects are included and when the spectrally gray approximation is used for treatment of radiative heat transfer.

Effect of Radiative Heat Transfer Factor on the Temperature Distribution of a First Stage Vane

2014 ◽  
Author(s):  
Hong Yin ◽  
Mingfei Li ◽  
Zhongran Chi ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Distribution ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Swirling Flow ◽  
Inlet Temperature ◽  
Radiative Effect ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

As the advanced heavy-duty gas turbine develops, the turbine inlet temperature and pressure have increased quite significantly to achieve better performance. The flow and heat transfer conditions of hot components including combustor and turbine become even more extreme than ever which need corresponding aerodynamic and cooling design development. The issue of combustor-turbine interaction has been proposed as a complicated research topic. Currently the hot streak, turbulence intensity, swirling flow, radiation are the four important factors for combustor-turbine interaction research according to the literature. Especially as the turbine inlet temperature increases, the radiative heat transfer plays a more and more important role. In this paper, a first stage vane is selected for the conjugate heat transfer simulation including radiative heat transfer since it is almost impossible to identify the radiative effect in experiment. The goal is to examine the effects of radiative heat flux and temperature increment caused by radiation. Several radiative factors including the inlet radiation, gas composition, vane surface emissivity and outlet reflection are investigated. The temperature distribution and heat flux enhancement under different conditions are compared, which can provide reference to the turbine heat transfer design. The general information of radiative effect can be summarized by quantitative analysis. Results show that the temperature increases obviously when considering the radiation effect as expected. However, these factors show distinct influence on the vane temperature distribution. The inlet radiation has significant impact on the vane leading edge and pressure side. Besides the gas radiation plays quite uniform on the whole vane surface.

Near-Field Radiative Heat Transfer Between Mie Resonance-Based Metamaterials Made of Coated Nonmagnetic Particles

2019 ◽  
Author(s):  
Lu Lu ◽  
Jinlin Song ◽  
Kun Zhou ◽  
Qiang Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Crystals ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Nematic Liquid Crystals ◽  
Near Field ◽  
Core Shell ◽  
Mie Resonance ◽  
Shell Particles

Abstract Near-field radiative heat transfer between Mie resonance-based metamaterials composed of SiC/d-Si (silicon carbide and doped silicon) core/shell particles immersed in aligned nematic liquid crystals are numerically investigated. The metamaterials composed of core/shell particles exhibit superior performances of enhanced heat transfer and obvious modulation effect when compared to that without shell. The underlying mechanism can be explained that the excitation of Fröhlich mode and epsilon-near-zero (ENZ) resonances both contribute to the total heat flux. Modulation of near-field radiative heat transfer can be realized with the host material of aligned nematic liquid crystals. The largest modulation ratio could be achieved as high as 0.45 for metamaterials composed of core/shell SiC/d-Si particles, and the corresponding heat flux is higher than other similar materials such as LiTaO3/GaSb and Ge/LiTaO3. While with the same volume filling fraction, the modulation ratio of that composed of SiC particles is only 0.2. We show that the core/shell nanoparticles dispersed liquid crystals (NDLCs) have a great potential in enhancing the near-field radiative heat transfer in both the p and s polarizations with the radii of 0.65 μm, and Mie-metamaterials are shown for the first time to modulate heat flux within sub-milliseconds.

Modeling Thermal Radiation With Focus on Particle Radiation in Grate Fired Furnaces Combusting MSW or Biomass: A Parametric Study

2013 ◽  
Author(s):  
Henrik Hofgren ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fly Ash ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Parametric Study ◽  
Radiative Heat ◽  
Size Distributions ◽  
Particle Radiation ◽  
Mass Size

This parametric study shows that thermal radiation from particles, fly ash and char, can be highly relevant for estimating the radiative heat flux to surfaces in grate fired furnaces, especially to the hot bed. The large effects of particle radiative heat transfer come from cases with municipal solid waste (MSW) as fuel whereas biomass cases have moderate effect on the overall radiative heat transfer. The parameters investigated in the study were the fuel parameters, representing a variety of particle loads and size distributions, emissivities of walls and bed, and the size of furnace. The investigations were conducted in a 3-D rectangular environment with a fixed temperature field, and homogeneous distribution of gases and particles. The choice of boundary emissivity was found to be much more or equally important as the particle radiation effects, dependent if biomass or MSW, respectively, was used as the fuel. The effect of particle radiation increased with increasing furnace size, mostly evident in the change of the radiative source term and the heat flux to the bed. Compared to previous studies of particle radiation in grate fired combustion, this study used realistic particle mass size distributions for fly ash. Estimates of char mass size distributions inside the furnace were conducted and used.

Prediction of Radiative Heat Transfer in Industrial Equipment Using the Radiation Element Method

2001 ◽  
Vol 123 (4) ◽  
pp. 530-536 ◽  
Author(s):  
Zhixiong Guo ◽  
Shigenao Maruyama
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Narrow Band ◽  
Particle Density ◽  
Three Dimensional ◽  
Wide Band ◽  
Band Model ◽  
Participating Media ◽  
Carbon Particles

The radiation element method by ray emission method, REM2, has been formulated to predict radiative heat transfer in three-dimensional arbitrary participating media with nongray and anisotropically scattering properties surrounded by opaque surfaces. To validate the method, benchmark comparisons were conducted against the existing several radiation methods in a rectangular three-dimensional media composed of a gas mixture of carbon dioxide and nitrogen and suspended carbon particles. Good agreements between the present method and the Monte Carlo method were found with several particle density variations, in which participating media of optical thin, medium, and thick were included. As a numerical example, the present method is applied to predict radiative heat transfer in a boiler model with nonisothermal combustion gas and carbon particles and diffuse surface wall. Elsasser narrow-band model as well as exponential wide-band model is adopted to consider the spectral character of CO2 and H2O gases. The distributions of heat flux and heat flux divergence in the boiler furnace are obtained. The difference of results between narrow-band and wide-band models is discussed. The effects of gas model, particle density, and anisotropic scattering are scrutinized.

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