Optical Constants of Soot and Their Application to Heat-Flux Calculations

1969 ◽  
Vol 91 (1) ◽  
pp. 100-104 ◽  
Author(s):  
W. H. Dalzell ◽  
A. F. Sarofim
Keyword(s):  
Heat Flux ◽  
Light Scattering ◽  
Absorption Coefficient ◽  
Room Temperature ◽  
Optical Constants ◽  
Soot Concentration ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient

Data on the room temperature optical constants of soot are presented for the wavelength regions 0.4–0.8μ and 2.5–10.0/μ. Dispersion formulas are developed for interpolating the data between 0.8 and 2.5μ. The results are used to calculate the spectral absorption coefficient and the total emissivities of soot suspensions. It is shown that the correct values of the optical constants are needed in the use of light-scattering techniques for the measurement of the soot concentration but that uncertainties introduced in flux calculations by use of approximate values of the optical constants are not greater than those introduced by the present uncertainties in the values of the soot concentration.

scholarly journals Simple methods for identification of radiative properties of highly-porous ceria ceramics in the range of semi-transparency

2017 ◽  
Vol 27 (5) ◽  
pp. 1108-1117 ◽  
Author(s):  
Leonid A. Dombrovsky ◽  
Wojciech Lipinski
Keyword(s):  
Absorption Coefficient ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Radiative Properties ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Content Type ◽  
Hemispherical Reflectance ◽  
Steady Oscillations ◽  
Highly Porous

Purpose The aim of this paper is to present advanced experimental–numerical methods for identification of spectral absorption and scattering properties of highly porous ceria ceramics in the range of semi-transparency at room and elevated temperatures. Design/methodology/approach At room temperature, a period of quasi-steady oscillations of the sample surface temperature generated in response to recurrent laser heating at fixed values of the maximum and minimum temperature of the irradiated surface is measured along with the normal-hemispherical reflectance. Radiative properties are then identified using a combined heat transfer model. At elevated temperatures, an analytical solution proposed in an earlier study for zirconia ceramics is used to retrieve spectral absorption coefficient of ceria ceramics from the measured normal emittance. Findings and Originality/value This method can be used to obtain small absorption coefficient of ceria ceramics at room temperature. The required measurements of both the normal-hemispherical reflectance and the period of quasi-steady oscillations of the irradiated surface temperature of the ceramics sample between fixed values of the maximum and minimum temperatures can be readily conducted using thermal laboratory equipment. Another method has been suggested for identification of the spectral absorption coefficient of ceria ceramics at elevated temperatures. This method is based on a relation between the measured normal emittance of an isothermal sample and the absorption coefficient.

Multi-Dimensional Radiative Transfer in Nongray Gases—General Formulation and the Bulk Radiative Exchange Approximation

1978 ◽  
Vol 100 (3) ◽  
pp. 486-491 ◽  
Author(s):  
S. S. Tsai ◽  
S. H. Chan
Keyword(s):  
Heat Flux ◽  
Radiative Transfer ◽  
Absorption Coefficient ◽  
Radiative Heat ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Multidimensional Problems ◽  
All Optical ◽  
Exchange Approximation ◽  
Radiative Exchange

The present paper presents a general formulation of the radiative heat flux and its divergence for multi-dimensional radiative problems involving nongray absorbing-emitting gases. The expressions obtained are in terms of total band absorptance rather than the spectral absorption coefficient. Thus the frequency integration is eliminated, and the expressions are more compact. They avoid the necessity of detailed spectral absorption coefficient data for radiative transfer computations. Also presented is the bulk radiative exchange approximation together with its refinement. It is proposed to circumvent the mathematical complexity inherently imbedded in nongray multidimensional problems. The approximation, which is valid in the optically thin and thick limits, is found to be general and useful, not only because of its simplicity, but also because of its accuracy in all optical conditions.

Effects of Radiative Transfer Modeling on Transient Temperature Distribution in Semitransparent Glass Rod

2003 ◽  
Vol 125 (4) ◽  
pp. 635-643 ◽  
Author(s):  
Zhiyong Wei ◽  
Kok-Meng Lee ◽  
Serge W. Tchikanda ◽  
Zhi Zhou ◽  
Siu-Ping Hong
Keyword(s):  
Heat Flux ◽  
Radiative Transfer ◽  
Absorption Coefficient ◽  
Radiative Energy ◽  
Transient Temperature ◽  
Band Model ◽  
Two Dimensional ◽  
Spectral Absorption ◽  
Short Wavelength Band ◽  
Spectral Absorption Coefficient

This paper presents a method of modeling the radiative energy transfer that takes place during the transient of joining two concentric, semitransparent glass cylinders. Specifically, we predict the two-dimensional transient temperature and heat flux distributions to a ramp input which advances the cylinders into a furnace at high temperature. In this paper, we discretize the fully conservative form of two-dimensional Radiative Transfer Equation (RTE) in both curvilinear and cylindrical coordinate systems so that it can be used for arbitrary axisymmetric cylindrical geometry. We compute the transient temperature field using both the Discrete Ordinate Method (DOM) and the widely used Rosseland’s approximation. The comparison shows that Rosseland’s approximation fails badly near the gap inside the glass media and when the radiative heat flux is dominant at short wavelengths where the spectral absorption coefficient is relatively small. Most prior studies of optical fiber drawing processes at the melting point (generally used Myers’ two-step band model at room temperature) neglect the effects of the spectral absorption coefficient at short wavelengths λ<3μm. In this study, we suggest a modified band model that includes the glass absorption coefficient in the short-wavelength band. Our results show that although the spectral absorption coefficient at short wavelengths is relatively small, its effects on the temperature and heat flux are considerable.

Spectral Absorption Coefficient of Molten Aluminum Oxide from.0.385 to 0.780 mum

1995 ◽  
Vol 78 (3) ◽  
pp. 583-587 ◽  
Author(s):  
J. K. Richard Weber ◽  
Shankar Krishnan ◽  
Collin D. Anderson ◽  
Paul C. Nordine
Keyword(s):  
Absorption Coefficient ◽  
Aluminum Oxide ◽  
Molten Aluminum ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient

scholarly journals The spectral absorption coefficient at 254 nm as a real-time early warning proxy for detecting faecal pollution events at alpine karst water resources

2010 ◽  
Vol 62 (8) ◽  
pp. 1898-1906 ◽  
Author(s):  
H. Stadler ◽  
E. Klock ◽  
P. Skritek ◽  
R. L. Mach ◽  
W. Zerobin ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Real Time ◽  
Early Warning ◽  
Data Communication ◽  
Spring Water ◽  
Karst Water ◽  
Spectral Absorption ◽  
Sampling Device ◽  
Spectral Absorption Coefficient ◽  
Faecal Pollution

Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005–2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254 nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper. Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n&gt;800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated.

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