ENCIT2012-118 NEW COEFFICIENTS OF THE WEIGHTED-SUM-OF-GRAY-GASES MODEL USING HITEMP 2010 DATABASE - PDF
Leonardo J. Dorigon, UFRGS, Brazil
Marcelo Galarça, IFRS, Brazil
Francis H. R. França, UFRGS, Brazil
Abstract: In this work, new coefficients for the WSGG model are proposed based on the up to date HITEMP 2010 database. The coefficients are determined for gas mixtures of water and carbon dioxide. The coefficients are obtained for partial pressure ratios pH2O/pCO2 of 1.0 and 2.0, simulating combustion products of fuel oil and methane. The path-length ranges from 0,001 atm\&\#8729;m to 10 atm\&\#8729;m, while the temperature varies between 400 K and 2500 K. This study also makes a comparison of the total emittance values obtained from the model with benchmark line-by-line (LBL) results, showing an excellent agreement. With the obtained coefficients, one-dimensional radiant heat transfer problems are solved in order to compare the solution obtained by the WSGG model with the solution obtained by the LBL integration. In the comparisons, different temperature profiles, temperature gradients and species concentrations are used. In all cases it is possible to verify the good agreement of the WSGG and LBL results.
Keywords:Radiation heat transfer; participating medium; weighted-sum-of-gray-gases.
Presentation Schedule: Thursday, 11:40-12:00. Session: HMT6. Presenter: Francis França.
ENCIT2012-208 ZONAL METHOD IMPLEMENTATION TO DETERMINE THE THERMAL RADIATION HEAT TRANSFER IN BIDIMENESIONAL FURNACES - PDF
Gleyzer Martins, Oscar Saul Mendoza Hernandez, Enio Pedone Bandarra Filho, UFU, Brazil
Abstract: The radiation heat transfer is relevant in the furnace and the combustion chambers, so that knowing the temperature distribution and the gas and soot concentration is possible to estimate the radiation heat transfer, thereby to evaluate the performance of the equipment. The zonal method with Weighted Sum Gray Gas - WSGG is a powerful methodology recommended by the accuracy and low computational cost, this in turn, consists in a division of the furnace volume in small isothermal volumes to estimate the direct exchange areas and the radiative heat transfer. In this paper was implemented three ways to determine the direct exchange areas using three different weighted sum of gray gas coefficients to an bi-dimensional black wall furnace with temperature and gases concentration profile known. The results show the discrete sum integration methods for direct exchange area with three coefficients of weighted sum of gray gases are the implementation most accurate and fast.
Keywords:Gas Concentration; Temperature Profile; Combustion Chambers.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-357 FINITE ELEMENT SIMULATION OF A 2-D NON-LINEAR HEAT TRANSFER PROBLEM USING A MINUMUM PRINCIPLE - PDF
Eduardo D. Corrêa, Rogério M. Saldanha da Gama, Luiz Mariano Carvalho, UERJ, Brazil
Maria Laura Martins-Costa, UFF, Brazil
Abstract: This article studies the steady-state conduction-radiation heat transfer in an opaque and convex rigid body at rest. The mechanical model gives rise to a second-order partial differential equation subjected to non-linear boundary conditions, treated as a sequence of linear problems, which are solved by employing the minimization of quadratic functionals, proposed in this work. A finite element method approximates this solution. Some numerical results illustrate the procedure.
Keywords:Conduction-radiation; variational principle; finite elements.
Presentation Schedule: Thursday, 12:20-12:40. Session: HMT6. Presenter: Rogério M. Saldanha da Gama.
ENCIT2012-036 RADIATIVE HEAT TRANSFER MODELING WITH HITEMP 2010 DATABASE USING CW AND SLW METHODS - PDF
Rogério Brittes, Fabiano Cassol, Francis H. R. França, UFRGS, Brazil
Cláudia A. L. Cardoso, UEM, Brazil
Abstract: The HITEMP 2010 spectral database is employed to obtain the necessary parameters for the prediction of radiative transfer in nonisothermal and homogeneous media. It is considered a one dimensional slab filled with 10 \% of carbon dioxide and 20 \% of water vapour. The spectral integration is performed with SLW and CW models and compared with line by line benchmark solution. It is observed that, for the thermal conditions and species concentrations considered, the SLW model is more suitable to predict the radiative heat source, which is one of the main parameters in the computation of radiation in the participating media.
Keywords:radiative transfer; spectral integration; HITEMP database; gas models.
Presentation Schedule: Thursday, 11:00-11:20. Session: HMT6. Presenter: Fabiano Cassol.
ENCIT2012-037 INFLUENCE OF SOOT PARTICULATE IN RADIATION HEAT TRANSFER USING THE GRAY GAS MODEL - PDF
Fabiano Cassol, Rogério Brittes, Francis H. R. França, UFRGS, Brazil
Cláudia A. L. Cardoso, UEM, Brazil
Abstract: The design accuracy involving combustion processes indicate energy savings and lower pollutants emission. Since radiation heat transfer is dominant in such processes, the thermal model requires an accurate modeling for gases, taking into account all the spectral properties. On the other hand, the particulate medium (soot) present in the emissions shows spectral properties with subtle variations and easy determinations. Thus, most simplistic spectral models solve the modeling of soot. This paper presents a radiative heat transfer solution in a one-dimensional slab formed by a participating medium composed of CO2, H2O and soot. It is considered the line-by-line solution and gray gas (GG) model to solve the participating medium. The contribution of this work is to demonstrate the soot spectral dominance properties in high concentrations as well as the possibility to use simple spectral models in combustion problems with high concentration of soot. In addition, this study also provides new correlations for the GG model based on HITEMP 2010 database.
Keywords:Radiation heat transfer; participating medium; gray gas; soot.
Presentation Schedule: Thursday, 12:00-12:20. Session: HMT6. Presenter: Fabiano Cassol.
ENCIT2012-132 THE MULTI-SPECTRAL BUNDLE MODEL FOR MONTE CARLO RADIATION HEAT TRANSFER COMPUTATION - PDF
André Maurente, Francis H. R. França, Horácio Antonio Vielmo, UFRGS, Brazil
Abstract: The Monte Carlo method is powerful in radiation heat transfer computations, since it is able to deal with complex geometries and scattering phenomena without highly increase the difficulties associated to the model implemen- tation. On the other hand, the Monte Carlo is highly computer time consuming, specially when necessary accounting for the detailed spectral behavior. The Monte Carlo, as other numerical techniques, can be applied with spectral models. Here we propose the Multi-Spectral Bundle model, which improves the computational efficiency of the Monte Carlo and can be applied in line-by-line computations as well as when spectral models are employed.
Keywords:Radiation heat transfer; non-uniform absorbing-emitting gases; Monte Carlo method; spectral model.; Radiation heat transfer, non-uniform absorbing-emitting gases, Monte Carlo method, spectral model..
Presentation Schedule: Thursday, 12:40-13:00. Session: HMT6. Presenter: André Maurente.
ENCIT2012-064 EVALUATION OF NEW WSGG MODEL CORRELATIONS ON RADIATIVE SOURCE TERM IN A 2D AXISYMMETRIC TURBULENT DIFFUSION FLAME - PDF
Felipe Roman Centeno, Fabiano Cassol, Leonardo J. Dorigon, Francis H. R. França, UFRGS, Brazil
Cristiano V. Silva, URI, Brazil
Abstract: In the present work, the radiation effect of non-gray gases were estimated by means of two different weighted-sum-of-gray-gases (WSGG) model correlations (classical ones of Smith et al. (1982) and new ones of Dorigon (2012) which were fitted from state-of-the-art gas spectroscopic database), in a turbulent diffusion methane-air cylindrical combustion chamber. The reaction rates were considered as minimum rates between Arrhenius and Eddy Breakup rates. A two step global reaction mechanism was used and turbulence modeling was considered via standard k-\&\#61541; model, since the stress is on radiation calculations. The source terms of energy equation consisted of reaction rates and radiation effects. The discrete ordinates method (DOM) was employed to solve the radiative transfer equation (RTE). Comparing the results obtained with the different WSGG correlations it was possible to check that the temperature, wall heat flux and radiant fraction were affected by the different WSGG correlations, while the influence on species concentrations were negligible. The numerical results obtained considering the new WSGG correlations were closer to the experimental data (Garréton and Simonin, 1994) than the case with the classical model.
Keywords:Radiation heat transfer; WSGG model; combustion; turbulent diffusion flames.
Presentation Schedule: Thursday, 11:20-11:40. Session: HMT6. Presenter: Felipe Roman Centeno.