Application of the Cumulative Wavenumber Approach for Modeling Radiative Transfer in H2O Under Non-Isothermal and Non-Homogeneous Conditions

2002 ◽  
Author(s):  
Vladimir P. Solovjov ◽  
Brent W. Webb
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Radiative Transfer ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Local Spectrum ◽  
Full Spectrum ◽  
Model Predictions ◽  
Spectrum Correlation ◽  
Spectral Database

Recently, the cumulative wavenumber approach was formulated and its viability demonstrated in predictions of radiative heat transfer in high temperature CO2. The approach allows for local spectrum correlation, rather than full-spectrum correlation as commonly done previously. This work reports on the generation of cumulative wavenumber data for H2O, and explores solutions using the cumulative wavenumber approach for water vapor (balance nitrogen) in homogeneous/non-isothermal media, and extends the technique to non-homogeneous/non-isothermal scenarios. Model predictions are compared with rigorous line-by-line benchmark integration of the Radiative Transfer Equation, with the same spectral database (HITEMP) used in both model and line-by-line benchmark predictions.

Reverse Monte-Carlo Ray-Tracing Method Combined With Full-Spectrum K-Distribution Method for Radiative Heat Transfer

2008 ◽  
Author(s):  
Xiaojing Sun ◽  
Philip J. Smith
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Ray Tracing ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Computational Effort ◽  
Simulation Methods ◽  
Full Spectrum ◽  
Distribution Method

Accurate prediction of radiative heat transfer plays a key role in many high temperature applications, such as combustion devices and fires. Among various simulation methods, the Monte-Carlo Ray-Tracing (MCRT) has the advantage of solving the radiative transfer equation (RTE) for real gas mixtures with almost no approximations; however, it has disadvantage of requiring a large computational effort. The MCRT method can be carried out with either the Forward MCRT or the Reverse MCRT, depending on the direction of ray tracing. The RMCRT method has advantages over the FMCRT method in that it uses less memory, and in a domain decomposition parallelization strategy, it can explicitly obtain solutions for the domain of interest without the need for the solution on the entire domain.

Radiative Heat Transfer in High-Pressure Laminar Hydrogen-Air Diffusion Flames Using Spherical Harmonics and K-Distributions

2012 ◽  
Author(s):  
Jian Cai ◽  
Shenghui Lei ◽  
Adhiraj Dasgupta ◽  
Michael F. Modest ◽  
Dan C. Haworth
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Water Vapor ◽  
Spherical Harmonics ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Diffusion Flames ◽  
Transport Equations ◽  
Full Spectrum ◽  
Air Jet

Radiative heat transfer is studied numerically for high-pressure laminar H2-air jet diffusion flames, with pressure ranging from 1 to 30 bar. Water vapor is assumed to be the only radiatively participating species. A full spectrum k-distribution spectral model is used. Narrowband k-distributions of water vapor are calculated and databased from the HITEMP 2010 database, which claims to retain accuracy up to 4000K. The full-spectrum k-distributions are assembled from their narrowband counterparts to yield high accuracy with little additional computational cost. The radiative transfer equation (RTE) is solved using various spherical harmonics methods, such as P1, simplified P3 (SP3) and simplified P5 (SP5). The resulting partial differential equations as well as other transport equations in the laminar diffusion flames are discretized with the finite-volume method in OpenFOAM. Differential diffusion effects which are important in laminar hydrogen flames are also included in the scalar transport equations. It was found that peak flame temperature becomes less sensitive to radiation at higher pressure, and that radiation causes cooling in the downstream region. Differences between the three spherical harmonics RTE solver were found negligible below 5 bar.

Sphere-to-Sphere Radiative Transfer Coefficient for Packed Sphere System

2001 ◽  
Author(s):  
S. H.-K. Lee ◽  
S. C.-H. Ip ◽  
A. K. C. Wu
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Transfer Coefficient ◽  
Radiative Heat Transfer ◽  
Transfer Equation ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Radiative Properties ◽  
Equation Approach ◽  
Packed Sphere

Abstract Rapid sintering is one of the most attractive metalworking technologies due to its ability to fabricate the final product with different microstructure in an economical manner. During this process, the high heating rate would induce a great thermal gradient to the sintering part. Such temperature differences affect the microstructure of the product, which in turn leads to the occurrence of microstructure defects. However, for this non-isothermal sintering, the present Radiative Transfer Equation approach or Units/Cells approach cannot effectively compute the temperature distributions inside the porous media, so as to predict the part defects. Cumbersome computations are needed for the Radiative Transfer Equation approach. For the Units/Cells approach, the use of regular assembly in the model limits the analysis of complex packed sphere systems. This study seeks to simplify the entire computational process for different packed sphere systems. By introducing a Radiative Transfer Coefficient (RTC) approach, the computation of radiative heat transfer within the porous bed can be enhanced. The newly introduced Radiative Transfer Coefficient is defined as the ratio of radiative energy exchange, including direct and indirect exchange, from the emitting sphere to the receiving sphere, which is a function of the system microstructure and radiative properties. A set of energy-balanced algebraic equations can then be established. With an appropriate initial energy guess for each sphere, these equations can be solved by the Gauss-Seidel iteration scheme, thereby computing the radiative heat transfer in packed sphere systems with different microstructures and radiative properties. The temperature for each sphere can therefore be computed right away. This model has been validated in different perspectives. With this RTC approach, the overall computational time required is significantly shorter, providing a set of fine-resolution temperature solution.

Multi-Scale Full-Spectrum k-Distribution Method for Radiative Transfer in Inhomogeneous Gas Mixtures With Wall Emission

2005 ◽  
Author(s):  
Liangyu Wang ◽  
Michael F. Modest
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Inhomogeneous Media ◽  
Full Spectrum ◽  
Distribution Method ◽  
Multi Scale ◽  
Original Distribution ◽  
Distribution Scheme ◽  
Inhomogeneous Gas

The multi-scale full-spectrum k-distribution (MSFSK) method has become a promising method for radiative heat transfer in inhomogeneous media. In this paper an original distribution scheme is proposed to extend the MSFSK’s ability in dealing with boundary wall emission. This scheme pursues the overlap concept of the MSFSK method and requires no changes in the original MSFSK formulation. A boundary emission overlap coefficient is introduced and two approaches of evaluating the coefficient are outlined. The distribution scheme is evaluated and the two approaches are compared by conducting sample calculations for radiative heat transfer in strongly inhomogeneous media using both the MSFSK method and the line-by-line method.

Accelerate Iteration of Least-Squares Finite Element Method for Radiative Heat Transfer in Participating Media With Diffusely Reflecting Walls

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Wei An ◽  
Tong Zhu ◽  
NaiPing Gao
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Boundary Condition ◽  
Finite Element ◽  
Radiative Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Present Model ◽  
Participating Media ◽  
Element Method

A high reflectivity of walls often leads to prohibitive computation time in the numerical simulation of radiative heat transfer. Such problem becomes very serious in many practical applications, for example, metal processing in high-temperature environment. The present work proposes a modified diffusion synthetic acceleration model to improve the convergence of radiative transfer calculation in participating media with diffusely reflecting boundary. This model adopts the P1 diffusion approximation to rectify the scattering source term of radiative transfer equation and the reflection term of the boundary condition. The corrected formulation for boundary condition is deduced and the algorithm is realized by finite element method. The accuracy of present model is verified by comparing the results with those of Monte Carlo method and finite element method without any accelerative technique. The effects of emissivity of walls and optical thickness on the convergence are investigated. The results indicate that the accuracy of present model is reliable and its accelerative effect is more obvious for the optically thick and scattering dominated media with intensive diffusely reflecting walls.

Markov Analysis of Radiative Transfer in Specular Enclosures

1991 ◽  
Vol 113 (2) ◽  
pp. 429-436 ◽  
Author(s):  
R. L. Billings ◽  
J. W. Barnes ◽  
J. R. Howell ◽  
O. E. Slotboom
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Markov Chains ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Previous Literature ◽  
Markov Analysis ◽  
Two Parameter

This paper is directed at the use of Markov chains in the modeling of radiative heat transfer in specular enclosures containing nonparticipating gases. Following a brief review of previous literature in that area of investigation, a two-parameter state definition is given. The analysis of general infinitely long enclosures using that definition is then discussed, and the paper concludes with a report of selected implementation results.

SLMB Modeling of the Full Spectrum Cumulative k-Distribution of H2O

2009 ◽  
Author(s):  
Fre´de´ric Andre´ ◽  
Rodolphe Vaillon
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Comprehensive Description ◽  
Full Spectrum ◽  
Reliable Technique ◽  
Gaseous Media ◽  
Energy Exchanges ◽  
Atmospheric Heat

Radiative heat transfer is significant in many applications involving energy exchanges in gaseous media, such as combustion in engines or furnaces, atmospheric heat balances,.. The Line-By-Line (LBL) approach is the most reliable technique to determine the radiative properties of gases but is rarely used in radiative transfer simulations due to the associated prohibitive computational requirements. Approximate models are favored for such calculations. A comprehensive description of these existing methodologies can be found in Refs. [1, 2].

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