Closure to “Discussions of ‘Thermal Radiation Characteristics of Cylindrical Enclosures’” (1962, ASME J. Heat Transfer, 84, p. 80)

1962 ◽  
Vol 84 (1) ◽  
pp. 81-81
Author(s):  
E. M. Sparrow ◽  
L. U. Albers ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiation Characteristics

Spectral Thermal Radiation Characteristics of Coal Ashes and Slags: Influence of Chemical Composition and Temperature

2003 ◽  
Author(s):  
S. Linka ◽  
S. Wirtz ◽  
V. Scherer
Keyword(s):  
Heat Transfer ◽  
Chemical Composition ◽  
Thermal Radiation ◽  
Coal Ash ◽  
Spectral Emissivity ◽  
Department Of Energy ◽  
Radiation Characteristics ◽  
Transfer Rates ◽  
Inorganic Species ◽  
Coal Ashes

During the combustion of pulverized coal, ash particles (formed from inorganic species) can deposit on heat-transfer surfaces, resulting in a decrease in heat transfer rates and system efficiency. In addition to the knowledge of the thermal conductivity of the deposits it is necessary to obtain information on the thermal radiation characteristics of the furnace walls to predict the influence of ash sedimentation on heat transfer. At the Department of Energy Plant Technology investigations on the spectral emissivity of different coal ashes and slags were performed applying a spectral radiometer. The samples were electrically heated. Temperatures were varied between 600 and 1400 °C. Emissivities in the range of wavelengths from 1 to 15 μm have been determined. An essential result is that coal ashes show selective thermal radiation characteristics. The main factor of influence on the emissivity is the chemical composition. Therefore, measurements on the single phases SiO2, Al2O3 and MgO were carried out and compared with the emissivity of typical coal ashes and slags. Furthermore, the emissivity depends on temperature, mainly in the wavelength range from 1 to 6 μm.

Thermal Radiation in Packed and Fluidized Beds

1988 ◽  
Vol 110 (4b) ◽  
pp. 1230-1242 ◽  
Author(s):  
C. L. Tien
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Fluidized Beds ◽  
Radiative Properties ◽  
Phase Boundaries ◽  
Radiation Characteristics ◽  
Theoretical Predictions ◽  
Systems Models ◽  
Reflectance Data

The present work gives an overview of the existing knowledge on radiative transfer in packed and fluidized beds. Special emphasis is given to the proper usage and determination of radiation characteristics of the particles in these systems. Models that treat the particulate bed as a continuum are discussed along with those that consider the system as discontinuous, i.e., accounting for the phase boundaries between the gas and the particles. Existing experimental techniques for determining the radiative properties are presented, and the published bed transmittance and reflectance data are discussed and compared with the theoretical predictions. Interaction of radiation with other modes of heat transfer is also examined.

scholarly journals Numerical Simulation of Heat Transfer Flow Subject to MHD of Williamson Nanofluid with Thermal Radiation

Symmetry ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 10
Author(s):  
Muhammad Amer Qureshi
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Thermal Radiation ◽  
Single Phase ◽  
Physical Parameters ◽  
Fundamental Symmetry ◽  
Box Scheme ◽  
Mhd Boundary Layer ◽  
Slippery Surface ◽  
Transfer Flow

In this paper, heat transfer and entropy of steady Williamson nanofluid flow based on the fundamental symmetry is studied. The fluid is positioned over a stretched flat surface moving non-uniformly. Nanofluid is analyzed for its flow and thermal transport properties by consigning it to a convectively heated slippery surface. Thermal conductivity is assumed to be varied with temperature impacted by thermal radiation along with axisymmetric magnetohydrodynamics (MHD). Boundary layer approximations lead to partial differential equations, which are transformed into ordinary differential equations in light of a single phase model accounting for Cu-water and TiO2-water nanofluids. The resulting ODEs are solved via a finite difference based Keller box scheme. Various formidable physical parameters affecting fluid movement, difference in temperature, system entropy, skin friction and Nusselt number around the boundary are presented graphically and numerically discussed. It has also been observed that the nanofluid based on Cu-water is identified as a superior thermal conductor rather than TiO2-water based nanofluid.

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