Evaluating the Ability of SLW Model in Numerical Simulation of Radiative Turbulent Reacting Flow in Industrial Application

2018 ◽  
Author(s):  
Masoud Darbandi ◽  
Mohammad Bagher Barezban ◽  
Gerry E. Schneider
Keyword(s):  
Absorption Coefficient ◽  
Radiation Absorption ◽  
Discrete Ordinates ◽  
Reacting Flow ◽  
Temperature Sensitive ◽  
Weighted Sum ◽  
Combustion Gases ◽  
Temperature Filed ◽  
Turbulent Closure ◽  
Wsgg Model

In this paper, the turbulent reacting flow in an industrial furnace is numerically simulated using the RANS equations. The two-equation standard k-ε and the eddy dissipation models are used respectively to close the turbulent closure problem and to consider the turbulence-chemistry interaction. The radiation transfer equation is solved using the discrete ordinates method (DOM). To calculate the radiation absorption coefficient in participating combustion gases, we use the spectral line-based weighted sum of grey gases (SLW) model and compare the achieved results with famous gray-based model, i.e., the weighted-sum-of-gray-gases (WSGG) model. The results of this research show that using the SLW model, the predicted heat transfer from the flame to the furnace walls is reduced due to the thermal radiation. So, the predicted temperature filed increases up to 5% near the outlet of furnace in comparison with the results of WSGG model, which is in more agreement with the experimental data. These results indicate that if one wishes to accurately predict the temperature field and the temperature sensitive quantities such as the NOx emission, one should use the spectral-based models to calculate the radiation absorption coefficient. The details are discussed in the results section.

Spectral Gas Absorption Coefficient Model Effects on Radiative Source Term in a 2D Axisymmetric Diffusion Flame

2010 ◽  
Author(s):  
Anderson C. Mossi ◽  
Vinayak V. Barve ◽  
Marcelo M. Galarc¸a ◽  
Hora´cio A. Vielmo ◽  
Francis H. R. Franc¸a ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Radiative Heat ◽  
Source Term ◽  
Computational Effort ◽  
Gas Absorption ◽  
Weighted Sum ◽  
Radiation Properties ◽  
Radiative Losses ◽  
Combustion Processes ◽  
Wsgg Model

A calculation of the radiative source term in combustion processes is an important part of the simulation process, because high temperatures are involved and the coupling of radiation to chemistry affects the overall flame characteristics. While relatively simple gas absorption coefficient models have been used in the recent past, it is becoming clearer that more accurate gas models alter the distribution of radiative sources in the flame. To accurately evaluate the radiative losses, it is necessary to use gas models in which the gas absorption coefficient is wavelength dependent. Such analyses can be computationally expensive depending on the particular treatment of the spectral dependence. It is important to understand the relative costs and benefits of different treatment of these effects. In this work, the divergence of the radiative heat flux is calculated for a two-dimensional cylindrical axisymmetric chamber using four different models: a simple gray gas model, the weighted-sum-of-gray-gases (WSGG) model, the spectral line-based weighted-sum-of-gray-gases (SLW) model, and the cumulative wavenumber (CW) model. The gray gas model and the WSGG model are widely used in recent studies and in most commercial software, because they are simple to implement and provide fast results. In general, however, they are not able to accurately predict the radiative losses. On the other hand, the SLW and CW models detail the variations of the absorption coefficient with the wavelength, and can give more accurate answers for the radiative source term, but require bigger computational effort. The divergence of the radiative flux predictions are compared with these four models, using temperature and concentration fields obtained from previous numerical simulations. The overall differences in radiation properties and in the overall cost of computations are detailed.

scholarly journals Synthesis and Characterisation of Thin Films of Bismuth Triiodide for Semiconductor Radiation Detectors

2014 ◽  
Vol 2014 ◽  
pp. 1-3 ◽  
Author(s):  
Alka Garg ◽  
Monika Tomar ◽  
Vinay Gupta
Keyword(s):  
Thin Films ◽  
Absorption Coefficient ◽  
Room Temperature ◽  
Active Material ◽  
Visible Region ◽  
Radiation Detectors ◽  
Radiation Absorption ◽  
X Rays ◽  
X Ray ◽  
Bismuth Iodide

Bismuth iodide is a potentially active material for room temperature radiation detector, as it is well reported in the literature that it has both wide energy band gap and high atomic absorption coefficient. Crystalline films of high atomic number and high radiation absorption coefficient can absorb the X-rays and convert them directly into electrical charges which can be read by imaging devices. Therefore, it was proposed to grow thin films of Bismuth iodide on glass substrate using thermal evaporation technique in vacuum to avoid the inclusion of impurities in the films. The structural studies of the films were carried out using XRD and optical absorption measurement was carried out in the UV/VIS region using spectrophotometer. All Bismuth iodide films grown at room temperature are polycrystalline and show X-ray diffraction peaks at angles reported in research papers. The optical transmission spectra of BiI3 films show a high transmission of about 80% in visible region with a sharp fall near the fundamental absorption at 650 nm. Resistivity of the as-grown film was found to be around 1012 ohm-cm suitable value for X-ray detection application. Films were subjected to scanning electron microscopy to study the growth features of both as-grown and annealed films.

Computational Analysis of Mixing in a Gas Turbine Combustor

2012 ◽  
Author(s):  
Alka Gupta ◽  
Mohamed Saeed Ibrahim ◽  
R. S. Amano
Keyword(s):  
Gas Turbines ◽  
Computational Analysis ◽  
Blunt Body ◽  
Mixture Fraction ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Equilibrium Mixture ◽  
Reacting Flow ◽  
Uniform Temperature ◽  
Combustion Gases

This paper presents the computational analysis of the dilution process involved in gas turbines order to cool the combustion gases to the desired temperature before it enters the turbine. Here, it should be noted that in order to focus only on the dilution process, non-reacting flow conditions were simulated and the complete system was reduced to mixing of a primary (hot) stream and dilution (cold) stream of air. Four different schemes were investigated based on the layout of the dilution holes and use of a blunt body. A complete three dimensional analysis was carried out for each case in order to investigate its effectiveness to produce a more uniform temperature conditions at the exit of the combustor, so as to reduce the detrimental effect these temperature non-uniformities have on the turbine blades. For comparison of the proposed schemes, a parameter is defined in terms of the temperatures of the dilution and primary flow streams at the inlet and the exit plane, called the mixture fraction. Based on this parameter, it was found that the staggered dilution holes with the blunt body has the mixture fraction closest to the equilibrium mixture fraction (0.4), which implies that this scheme with the mixture fraction of 0.36, resulted in best mixing and produced the most uniform temperature distribution at the exit amongst the four proposed schemes.

scholarly journals Extension of Weighted Sum of Gray Gas Data to Mathematical Simulation of Radiative Heat Transfer in a Boiler with Gas-Soot Media

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Samira Gharehkhani ◽  
Ali Nouri-Borujerdi ◽  
Salim Newaz Kazi ◽  
Hooman Yarmand
Keyword(s):  
Heat Transfer ◽  
Absorption Coefficient ◽  
Radiative Heat ◽  
Measured Data ◽  
Weighted Sum ◽  
Gas Temperature ◽  
Zone Method ◽  
Plant Site ◽  
Good Agreement ◽  
Steam Production

In this study an expression for soot absorption coefficient is introduced to extend the weighted-sum-of-gray gases data to the furnace medium containing gas-soot mixture in a utility boiler 150 MWe. Heat transfer and temperature distribution of walls and within the furnace space are predicted by zone method technique. Analyses have been done considering both cases of presence and absence of soot particles at 100% load. To validate the proposed soot absorption coefficient, the expression is coupled with the Taylor and Foster's data as well as Truelove's data for CO2-H2O mixture and the total emissivities are calculated and compared with the Truelove's parameters for 3-term and 4-term gray gases plus two soot absorption coefficients. In addition, some experiments were conducted at 100% and 75% loads to measure furnace exit gas temperature as well as the rate of steam production. The predicted results show good agreement with the measured data at the power plant site.

scholarly journals Gamma?Radiation Absorption Coefficients of Various Materials Allowing for Bremsstrahlung and Other Secondary Radiations

1961 ◽  
Vol 14 (4) ◽  
pp. 443 ◽  
Author(s):  
JW Allison
Keyword(s):  
Absorption Coefficient ◽  
Energy Loss ◽  
Basic Assumption ◽  
Radiation Energy ◽  
Radiation Absorption ◽  
Annihilation Radiation ◽  
Total Absorption ◽  
Absorption Coefficients ◽  
Radiation Energy Loss ◽  
Total Absorption Coefficient

Existing calculations of the total absorption coefficient are generally based on the assumption that all the primary radiation energy which is converted into Comptonscattered radiation escapes from the material without significant absorption. This paper extends this basic assumption to include fluorescent and annihilation radiation and bremsstrahlung, and new values of the photoelectric, Compton, pair production, and total absorption coefficients are determined in the energy range O� 01-100 MeV for hydrogen, nitrogen, oxygen, argon, aluminium, iron, lead, air, and water. For comparison purposes revised values of the total absorption coefficient, allowing for the Compton radiation energy loss only, are also determined for these materials, using the most recent data for the component coefficients.

WSGG Model Correlations to Compute Nongray Radiation From Carbon Monoxide in Combustion Applications

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Rogério Brittes ◽  
Felipe Roman Centeno ◽  
Aline Ziemniczak ◽  
Francis. H. R. França
Keyword(s):  
Carbon Monoxide ◽  
Total Pressure ◽  
Test Cases ◽  
Weighted Sum ◽  
Path Lengths ◽  
Nonisothermal Conditions ◽  
Wsgg Model

This paper presents correlations for the weighted-sum-of-gray-gases (WSGG) model for carbon monoxide based on HITEMP2010. The correlations are valid for pressure path lengths from 0.0001 atm·m up to 10 atm·m, total pressure in the order of 1.0 atm, and for temperatures ranging from 400 K up to 2500 K. Some test cases embodying nonhomogeneous, nonisothermal conditions are presented, and the results for the WSGG model are compared with the line-by-line (LBL) solutions for CO.

Field Validation of a Systematic Approach to Modeling of Glass Delivery Systems

2002 ◽  
Author(s):  
Christopher Q. Jian ◽  
Muralidharan ◽  
Abhijit Dutta
Keyword(s):  
Turbulent Flows ◽  
Molten Glass ◽  
Business Environment ◽  
Delivery Systems ◽  
Discrete Ordinates ◽  
Reacting Flow ◽  
Waste Generation ◽  
Front End ◽  
Future System ◽  
System Designs

In the fiberglass production process, glass is produced from various batch ingredients in a glass furnace. The molten glass is then delivered, through a delivery system that is often called the front-end system, to the various downstream forming operations. Front-end systems consist of various covered channels and forehearths. One of the major tasks of a front-end system is to insure that the glass is conditioned to the stringent specifications required by the forming operations. Improperly designed and/or operated front-end delivery systems can cause a number of problems to the forming operations, ranging from poor conversion efficiency (resulting in waste generation) due to glass defects to shortened service life. In today’s business environment, improvement in productivity, reduction in energy consumption, and minimization or elimination of waste generation have become priorities in managing and optimizing manufacturing operations. CFD has become an increasingly important tool for glass manufacturers to guide and optimize such system designs and operations. The current front-end model is developed to simultaneously simulate the chemically reacting turbulent flows in the superstructure and the laminar glass flow with strong buoyancy effects. Radiation from the superstructure wall surfaces and burner flames and internal radiation within the glass is modeled with the discrete ordinates (DO) radiation model in FLUENT. The turbulent reacting flow in the combustion space is calculated to obtain the flame shapes and lengths to accurately determine the heat transfer rate to the molten glass. The laminar glass flow, which is strongly influenced by natural convection, is calculated with temperature dependent physical properties. Simulations of the two radically different flow regimes are coupled through the interface boundary conditions in terms of temperature and heat flux continuity. Significant efforts were made to validate this approach with field measurements. Vertical temperature profiles were obtained in the glass melt as well as the combustion space at several strategically selected locations. The measurements were performed using two 6-element thermocouples housed in a platinum sheath. This coupled approach is expected to provide an effective tool that can be used to guide field operations as well as future system designs.

Modeling AlGaN p-i-n photodiodes

Doklady BGUIR ◽  
2022 ◽  
Vol 19 (8) ◽  
pp. 50-57
Author(s):  
N. N. Vorsin ◽  
A. A. Gladyshchu ◽  
T. L. Kushner ◽  
N. P. Tarasiuk ◽  
S. V. Chugunov ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Band Gap ◽  
Layer Thickness ◽  
Transition Matrix ◽  
Carrier Lifetime ◽  
Relevant Literature ◽  
Radiation Absorption ◽  
Comsol Multiphysics ◽  
Spontaneous Recombination ◽  
Peak Sensitivity

Ternary AlGaN alloys with a band gap of 3.4 to 6.2 eV are very promising for photodetectors in the UV wavelength range. Using the COMSOL MULTIPHYSICS software based on AlGaN, a p-i-n photodiode model was developed, including its I–V characteristic, spectral sensitivity of the received radiation, absorption coefficient as a function of the aluminum fraction and the depletion layer thickness. To calculate the process of interaction of a semiconductor with EM radiation, we used a model based on the use of an element of the transition matrix through the carrier lifetime during spontaneous recombination. In this case, the peak sensitivity of the photodiode is from 0.08 to 0.18 A/W at wavelengths of 0.2–0.33 µm. This is in line with experimental results taken from the relevant literature.

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