scholarly journals Optimal Band Selection for the Calculation of Planck Mean Absorption Coefficients

2017 ◽  
Vol 4 (1) ◽  
pp. 70-73
Author(s):  
M. Gnybida ◽  
Ch. Rümpler ◽  
V. R. T. Narayanan
Keyword(s):  
Temperature Profile ◽  
Low Voltage ◽  
Optimization Procedure ◽  
Optimal Number ◽  
Discrete Ordinates ◽  
Radiation Balance ◽  
Absorption Coefficients ◽  
Loss Mechanism ◽  
Spectral Solution ◽  
Dependent Absorption

Radiative heat transfer is a major heat loss mechanism in thermal plasmas generated during arc flashes/faults in switchgear applications or during high current interruption in low voltage circuit breakers. A common way to calculate the radiation balance is by means of approximate non-gray radiation models like P1 or discrete ordinates (DOM), where the frequency dependent absorption and emission are described in a number of frequency intervals (bands) using a constant absorption coefficient in each band. Current work is focused on finding the optimal number of bands as well as band interval boundaries that provide a reasonable level of accuracy in comparison to a full spectral solution. An optimization procedure has been applied to different SF<sub>6</sub> and copper vapor gas mixtures for an assumed temperature profile. Radiation model results using optimized band averaged absorption coefficients as well as spectral values are provided and discussed for the exemplary temperature profile.

scholarly journals Radiative Properties and Numerical Modeling of C4F7N-CO2-O2 Thermal Plasma

2019 ◽  
Vol 6 (2) ◽  
pp. 144-147
Author(s):  
M. Gnybida ◽  
Ch. Ruempler ◽  
V. R. T. Narayanan
Keyword(s):  
Thermal Plasma ◽  
Spectral Band ◽  
Optimization Procedure ◽  
Optimal Number ◽  
Radiative Properties ◽  
Absorption Coefficients ◽  
Medium Voltage ◽  
Spectral Bands ◽  
Computational Fluid Dynamics Cfd ◽  
Low Global Warming Potential

C<sub>4</sub>F<sub>7</sub>N and C<sub>4</sub>F<sub>7</sub>N-CO<sub>2</sub> mixtures are considered as alternatives to SF<sub>6</sub> for use in medium voltage gas insulated switchgear applications (GIS), due to the low global warming potential and good dielectric properties of C<sub>4</sub>F<sub>7</sub>N. Current work is focused on the calculation of radiative properties (absorption coefficients) of C<sub>4</sub>F<sub>7</sub>N-CO<sub>2</sub> thermal plasma and computational fluid dynamics (CFD) simulations of free burning C<sub>4</sub>F<sub>7</sub>N-CO<sub>2</sub> arcs that are stabilized by natural convection. Absorption coefficients of C<sub>4</sub>F<sub>7</sub>N-CO<sub>2</sub> plasma used in the CFD model are derived from spectral absorption coefficients by Planck averaging. An optimization procedure has been applied to find the optimal number of spectral bands as well as spectral band interval boundaries. Radiation and flow model results for C<sub>4</sub>F<sub>7</sub>N-CO<sub>2</sub> in comparison to SF<sub>6</sub> and air are provided and discussed.

Optical Response of Mixed Molybdenum Dichalcogenides for Solar Cell Applications Using the Modified Becke–Johnson Potential

2016 ◽  
Vol 71 (3) ◽  
pp. 213-223 ◽  
Author(s):  
Ushma Ahuja ◽  
Ritu Joshi ◽  
D.C. Kothari ◽  
Harpal Tiwari ◽  
K. Venugopalan
Keyword(s):  
Solar Cell ◽  
Dielectric Constants ◽  
Full Potential ◽  
Energy Bands ◽  
Absorption Coefficients ◽  
Augmented Plane Wave ◽  
Wave Technique ◽  
Degree Of Anisotropy ◽  
Dependent Absorption ◽  
First Time

AbstractEnergy bands and density of states (DOS) of mixed molybdenum dichalcogenides like MoS2, MoSeS, MoSe2, MoTe2, MoTeS, and MoTe0.5S1.5 are reported for the first time using the Tran–Blaha modified Becke–Johnson potential within full potential-linearised augmented plane wave technique. From the partial DOS, a strong hybridisation between the Mo-d and chalcogen-p states is observed below the Fermi energy EF. In addition, the dielectric constants, absorption coefficients, and refractivity spectra of these compounds have also been deduced. The integrated absorption coefficients derived from the frequency-dependent absorption spectra within the energy range of 0–4.5 eV show a possibility of using molybdenum dichalcogenides, particularly MoTe0.5S1.5, in solar cell applications. Birefringence and degree of anisotropy are also discussed using the data on refractivity and imaginary components of the dielectric constant.

scholarly journals A location optimization method for aircraft weakly-rigid structures

2014 ◽  
Vol 5 ◽  
pp. A18
Author(s):  
Zhong-Qi Wang ◽  
Yuan Yang ◽  
Yong-Gang Kang ◽  
Zheng-Ping Chang
Keyword(s):  
Optimization Procedure ◽  
Optimization Method ◽  
Optimal Number ◽  
Deformation Analysis ◽  
Element Analysis ◽  
Application Study ◽  
Location Optimization ◽  
Large Size ◽  
Analysis Theory ◽  
Nonlinear Programming Methods

Since aircraft weakly-rigid structure has large size and weak stiffness, there has serious deformation during assembly process. The current deformation analysis theory of rigid assembly is not applicable. Based on the N-2-1 (N > 3) locating principle, this paper presents a methodology for weakly-rigid parts. An optimization algorithm combines finite element analysis and nonlinear programming methods to find the optimal number and position of the locating points in order to minimize the assembly deformation. An example application study is presented to demonstrate the optimization procedure and its effectiveness by using the software of ABAQUS.

scholarly journals Angle-Dependent Absorption of Sound on Porous Materials

Acoustics ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 753-765
Author(s):  
Jose Cucharero ◽  
Tuomas Hänninen ◽  
Tapio Lokki
Keyword(s):  
Sound Absorption ◽  
Glass Wool ◽  
Room Acoustics ◽  
Sound Waves ◽  
Absorption Coefficients ◽  
Reverberation Chamber ◽  
Impedance Tube ◽  
Material Development ◽  
Dependent Absorption ◽  
Good Agreement

Sound-absorbing materials are usually measured in a reverberation chamber (diffuse field condition) or in an impedance tube (normal sound incidence). In this paper, we show how angle-dependent absorption coefficients could be measured in a factory-type setting. The results confirm that the materials have different attenuation behavior to sound waves coming from different directions. Furthermore, the results are in good agreement with sound absorption coefficients measured for comparison in a reverberation room and in an impedance tube. In addition, we introduce a biofiber-based material that has similar sound absorption characteristics to glass-wool. The angle-dependent absorption coefficients are important information in material development and in room acoustics modeling.

Investigation of Lightpipe Volumetric Radiation Effects in RTP Thermometry

2005 ◽  
Author(s):  
D. J. Frankman ◽  
B. W. Webb ◽  
M. R. Jones
Keyword(s):  
Radiative Transfer ◽  
Temperature Measurement ◽  
Temperature Profile ◽  
Radiation Effects ◽  
Measurement Techniques ◽  
Physical Contact ◽  
Spectral Variation ◽  
Wafer Temperature ◽  
Spectral Solution ◽  
Semitransparent Medium

A major obstacle to the widespread implementation of Rapid Thermal Processing (RTP) is the challenge of wafer temperature measurement. Frequently, lightpipe radiation thermometers are used to measure wafer temperatures in RTP reactors. While the lightpipe distorts the wafer temperature profile less than temperature measurement techniques which require physical contact, the presence of the lightpipe influences the wafer temperature profile. This paper presents the results of a theoretical study exploring that influence. The coupled radiation/conduction transport in the lightpipe enclosure is solved numerically. Radiation transfer in the system is modeled with varying levels of rigor, ranging from a simple volumetrically non-participating treatment to a full spectral solution of the Radiative Transfer Equation. The results reveal a rather significant effect of the lightpipe on the wafer temperature, which depends on the separation between the lightpipe tip and the wafer. The study illustrates clearly the need to model the lightpipe as a volumetrically participating, semitransparent medium, and further, the importance of accounting for spectral variation of the lightpipe properties in the prediction of the radiative transfer. Finally, two primary mechanisms are identified by which the lightpipe affects the wafer temperature distribution.

Investigation of Lightpipe Volumetric Radiation Effects in RTP Thermometry

2005 ◽  
Vol 128 (2) ◽  
pp. 132-141 ◽  
Author(s):  
David J. Frankman ◽  
Brent W. Webb ◽  
Matthew R. Jones
Keyword(s):  
Radiative Transfer ◽  
Temperature Measurement ◽  
Temperature Profile ◽  
Radiation Effects ◽  
Measurement Techniques ◽  
Constant Heat Flux ◽  
Physical Contact ◽  
Spectral Variation ◽  
Wafer Temperature ◽  
Spectral Solution

A major obstacle to the widespread implementation of rapid thermal processing (RTP) is the challenge of wafer temperature measurement. Frequently, lightpipe radiation thermometers are used to measure wafer temperatures in RTP reactors. While the lightpipe distorts the wafer temperature profile less than temperature measurement techniques which require physical contact, the presence of the lightpipe influences the wafer temperature profile. This paper presents the results of a theoretical study exploring that influence for an idealized RTP reactor in which the wafer is treated as a nonconducting, opaque, constant-heat-flux surface imaged by the lightpipe. The coupled radiation/conduction transport in the lightpipe measurement enclosure is solved numerically. Radiation transfer in the system is modeled with varying levels of rigor, ranging from a simple volumetrically nonparticipating treatment to a full spectral solution of the radiative transfer equation. The results reveal a rather significant effect of the lightpipe on the wafer temperature, which depends on the separation between the lightpipe tip and the wafer. The study illustrates clearly the need to model the lightpipe as a volumetrically participating, semitransparent medium, and further, the importance of accounting for spectral variation of the lightpipe properties in the prediction of the radiative transfer. Finally, two primary mechanisms are identified by which the lightpipe affects the wafer temperature distribution.

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