Search for: radiative-transfer
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    Effective compton cross section in non-degenerate high-temperature media

    , Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 95, Issue 1 , 2005 , Pages 61-69 ; 00224073 (ISSN) Shekh Momeni, F ; Samimi, J ; Sharif University of Technology
    The effective compton cross section in a non-degenerate plasma (n≪{((kT/c)2 + 2mkT)/h2}3/2) is investigated in a wide range of temperatures. The results show a decreasing behavior with temperatures especially for kT ≫ mec2. The results may be important in phenomena like accretion discs or ultra-relativistic blast waves in GRB models, where the emitted radiation has to pass through a medium containing high-energy electrons. © 2004 Elsevier Ltd. All rights reserved  

    Application of an optimized SLW model to calculation of non-gray radiation heat transfer in a furnace

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 13 November 2015 through 19 November 2015 ; Volume 8B-2015 , 2015 ; 9780791857502 (ISBN) Darbandi, M ; Abrar, B ; Schneider, G. E
    The spectral line based weighted sum of gray gases (SLW) model is considered as an advanced model, which can solve the radiative transfer equation (RTE) in non-gray participating media by dividing the absorption cross section spectrum into a limited number of intervals. Each interval is then treated as a gray gas medium, in which the attributed RTE should be solved separately. Therefore, the SLW model would be computationally more efficient than the other non-gray participating media solvers because it is faced with a small number of RTE solutions. In this work, we present a novel optimized SLW model and applied it to radiation heat transfer calculation in a model furnace. The current... 

    Advances in non-gray radiation calculation in combusting environments using a modified reference approach

    , Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 54, Issue 9 , 2018 , Pages 2705-2713 ; 09477411 (ISSN) Darbandi, M ; Abrar, B ; Sharif University of Technology
    Springer Verlag  2018
    The radiative heat transfer should be calculated very accurately in many combustion domains. This work uses the spectral-line based weighted-sum-of-gray-gases (SLW) model to calculate the radiation heat transfer in a model furnace representing a combustion field with high temperature gradient variations. The past researchers have commonly implemented the reference approach in the SLW model. However, the reference approach produces error because of enforcing a reference temperature to perform the non-gray radiation heat transfer calculations in non-isothermal domains. In this work, we implement a modified reference approach, which reduces such errors in non-gray gas calculations. We show that... 

    Thermal radiation transfer calculations in combustion fields using the SLW model coupled with a modified reference approach

    , Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 205 , 2018 , Pages 105-113 ; 00224073 (ISSN) Darbandi, M ; Abrar, B ; Sharif University of Technology
    Elsevier Ltd  2018
    The spectral-line weighted-sum-of-gray-gases (SLW) model is considered as a modern global model, which can be used in predicting the thermal radiation heat transfer within the combustion fields. The past SLW model users have mostly employed the reference approach to calculate the local values of gray gases’ absorption coefficient. This classical reference approach assumes that the absorption spectra of gases at different thermodynamic conditions are scalable with the absorption spectrum of gas at a reference thermodynamic state in the domain. However, this assumption cannot be reasonable in combustion fields, where the gas temperature is very different from the reference temperature.... 

    Application of the Active Learning Method for the estimation of geophysical variables in the Caspian Sea from satellite ocean colour observations

    , Article International Journal of Remote Sensing ; Volume 28, Issue 20 , 2007 , Pages 4677-4683 ; 01431161 (ISSN) Shahraiyni, T ; Schaale, M ; Fell, F ; Fischer, J ; Preusker, R ; Vatandoust, M ; Shouraki, B ; Tajrishy, M ; Khodaparast, H ; Tavakoli, A ; Sharif University of Technology
    Taylor and Francis Ltd  2007
    Remotely sensed data inherently contain noise. The development of inverse modelling methods with a low sensitivity to noise is in demand for the estimation of geophysical variables from remotely sensed data. The Active Learning Method (ALM) is well known to have a low sensitivity to noise. For the first time, ALM was utilized for the inversion of radiative transfer calculations with the aim of estimating chlorophyll a (Chl a), coloured dissolved organic matter (CDOM), and suspended particulate matter (SPM) in the Caspian Sea using MERIS (MEdium Resolution Imaging Spectrometer) data. ALM training is straightforward and fast. The ALM inversion models revealed the most relevant variables and... 

    Analytical solution for large amplitude vibrations of microbeams actuated by an electro-static force

    , Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1499-1507 ; 10263098 (ISSN) Baghani, M ; Asgarshamsi, A ; Goharkhah, M ; Sharif University of Technology
    Sharif University of Technology  2013
    An analytical study using Variational Iteration Method (VIM) is carried out in order to investigate the vibrations of electro-statically actuated double-clamped and simply-supported microbeams. Effects of applied voltage and residual axial load on the nonlinear natural frequency and deflection of the microbeams are studied. It shows that pre-compression in microbeams increases the amplitude of deflections for a specific applied voltage. Also, an increase in pre-tension motivates the microbeam to show more nonlinear behavior in an applied voltage. Predicted results are compared with the experimental data available in the literature and also with numerical results which shows a good agreement.... 

    On a generalized basis for solving the one dimensional transport equation: Theory

    , Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 113, Issue 5 , 2012 , Pages 335-341 ; 00224073 (ISSN) Ayyoubzadeh, S. M ; Vosoughi, N ; Sharif University of Technology
    The most general basis for approximating the transport equation has been studied. The application of the Gram-Schmidt procedure has been shown to unify the complete class of functions (polynomial type or non-polynomial type), applicable to this equation. The completeness of the series of functions is proved. A generalized version of the Fick's law is introduced. It is shown that the spectrum of the transport equation obtained by this method agrees with the conventional methods of obtaining the spectrum  

    Evaluating the ability of slw model in numerical simulation of radiative turbulent reacting flow in industrial application

    , Article ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting, FEDSM 2018, 15 July 2018 through 20 July 2018 ; Volume 2 , 2018 ; 08888116 (ISSN); 9780791851562 (ISBN) Darbandi, M ; Barezban, M. B ; Schneider, G. E ; Fluids Engineering Division ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2018
    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... 

    Solving combined natural convection-radiation in participating media considering the compressibility effects

    , Article 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 ; 13- 17 January , 2014 ; ISBN: 9781624102561 Darbandi, M ; Abrar, B ; Schneider, G. E ; Sharif University of Technology
    In this work, we aim to study the effect of temperature gradients on the combined natural convection-radiation heat transfer problem in participating media. To impose this combined effect, we first solve the radiative transfer equation in an absorbing and emitting media. Then, we suitably add the radiation source terms to the energy equation and solve the fluid flow equations. Literature shows that many incompressible algorithms use the Boussinesq assumption to model the thermobuoyant force; however, the validity of this assumption is limited to cases with low temperature gradient distributions. Evidently, Boussinesq assumption would result in considerable errors in high temperature gradient... 

    Reacting turbulent flow simulation to improve the mixing process in an oil refinery incinerator

    , Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM ; Vol. 1C, issue , August , 2014 ; ISBN: 9780791846230 Darbandi, M ; Abrar, B ; Barezban, M. B ; Faridvand, A ; Schneider, G. E ; Sharif University of Technology
    Combustion emission is one of the most important issues in the design of industries. Todays' strict environmental standards have limited the productions of CO, NOx, SOx, and other hazardous pollutants from the related industries. In this work, we study a typical oil refinery incinerator, which is used to burn waste gases residue produced during bitumen production process. The waste gas mainly includes a mixture including N2, H2O-vapor, and O2 species. Additionally, there are significant amounts of CO species and CxHy droplets in the waste gas composition. The measurements show that the CO emission becomes so crucial in high flow rate of feeding waste gas to the incinerator. Here, we... 

    Radiative heat transfer modeling in numerical simulation of a heavy duty steam generator

    , Article 54th AIAA Aerospace Sciences Meeting, 2016, 4 January 2016 through 8 January 2016 ; 2016 ; 9781624103933 (ISBN) Darbandi, M ; Abrar, B ; Barezban, M. B ; Schneider, G.E ; Shamsaei, Y ; Nematollahi, M ; Sharif Universty of Technology
    American Institute of Aeronautics and Astronautics Inc, AIAA 
    The proper modeling of radiation is of great importance in numerical simulation of combustion processes. A simple gray weighted-sum-of-gray-gases (WSGG) model has been intensively used in CFD simulations of industrial combustion applications, mainly because of its low computational costs. However, the gray assumption is far from the real behavior of non-gray combustion gases. This could consequently affect the accuracy of temperature field and heat flux distribution predictions. On the other hand, modern non-gray global radiation models such as the standard spectral line-based weighted-sum-od-gray-gases (SLW) model are still computationally expensive for many engineering purposes. To... 

    EAF heat recovery from incident radiation on water-cooled panels using a thermophotovoltaic system: a conceptual study

    , Article Steel Research International ; Volume 89, Issue 4 , 2018 ; 16113683 (ISSN) Saboohi, Y ; Fathi, A ; Skrjanc, I ; Logar, V ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    In this paper, a conceptual study and quantification of using a thermophotovoltaic system (TPV) to convert incident radiation on furnace panels to electrical energy is presented. In typical electric arc furnaces (EAF), a considerable amount of energy is wasted during the melting process, that is, steel enthalpy, off-gas extraction, vessel cooling, slag enthalpy, and others. Although a remarkable share of the energy is wasted in circulating water, the contained exergy is simply too low to be considered for heat recovery (under 0.5% of input exergy) in comparison to energy content of the extracted gasses and slag. In the performed study, a TPV power output is calculated as a function of arc... 

    Numerical simulation of mixing and heat transfer in an integrated centrifugal microfluidic system for nested-PCR amplification and gene detection

    , Article Sensors and Actuators, B: Chemical ; Volume 283 , 2019 , Pages 831-841 ; 09254005 (ISSN) Naghdloo, A ; Ghazimirsaeed, E ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2019
    Nucleic acid amplification via polymerase chain reaction (PCR) is one of the essential and powerful methods used in a myriad of bio-assays in clinical laboratories. Application of microfluidic devices in biologically-related processes like PCR can result in the usage of less volume of reactant samples and reduce the processing time. By implementing PCR systems on centrifugal microfluidic platforms, automation and portability can be easily achieved. Although several methods have been developed, most of them are still dealing with challenges of the required high processing time. This study presents the numerical simulation of a fully automated PCR system with the goal of enhancing the mixing... 

    Effect of oxygen enrichment in spectral thermal radiation in an unconfined turbulent bluff-body flame

    , Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 247 , 2020 Darbandi, M ; Barezban, M. B ; Fatin, A ; Bordbar, H ; Sharif University of Technology
    Elsevier Ltd  2020
    Oxy-fuel combustion is a modern carbon capture and storage (CCS) technique that improves the combustion process and reduces the environmental penalty of many combustion systems. Evidently, the accurate radiative calculation of oxy-fuel combustion is very important to obtain more improved combustion system designs with less environmental drawbacks. In the present study, a small scale unconfined turbulent bluff-body flame is numerically simulated to calculate the gas radiative properties using three different approaches of ignoring radiation, applying a modified version of the weighted sum of gray gases (WSGG) model, and employing the spectral line based weighted sum of gray gases (SLW) model....