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COB53 ESTIMATING ABSORPTION AND SCATTERING COEFFICIENTS AND INTERNAL SOURCE TERM IN A RADIATIVE TRANSFER PROCESS 1

Stephan Stephany^? , Haroldo Fraga de Campos Velho^? , Fernando Manuel Ramos^? & Curtis D. Mobley^??

? Laborat'orio Associado de Computa¸c~ao e Matem'atica Aplicada (LAC) Instituto Nacional de Pesquisas Espaciais (INPE), Caixa Postal 515, CEP 12201-970 -- S~ao Jos'e dos Campos (SP), BRASIL, e-mail: [stephan,fernando,haroldo]@lac.inpe.br

?? Sequoia Scientific, Inc., 9725 SE 36th Street, Suite 308 Mercer Island, WA 98040, USA, e-mail: mobley@sequoiasci.com

A reconstruction technique for estimation of inherent optical properties (IOPs) and bioluminescence sources in natural waters from in situ irradiance data is presented. The inverse problem is formulated as a nonlinear constrained optimization problem, assuming that the bioluminescence unknown profile can be represented by a sum of distributed gaussian sources. The objective function is defined as the square Euclidean norm of the difference vector between experimental and computed data. The associated direct problem is tackled with the Hydrolight 3.0 code, which uses the invariant imbedding theory.

Keywords: Inverse problems, inherent optical properties, bioluminescence sources, invariant imbedding method, radiative transfer equation.

COB234 THERMAL RADIATION IN COMBUSTION SYSTEMS

José Bezerra Pessoa Filho

Divisão de Sistemas Espaciais, CTA/Instituto de Aeronáutica e Espaço,

CEP 12228-904 São José dos Campos, SP, Brasil - E-mail: jbp@ase2.iae.cta.br

A numerical procedure for solving the nongray radiative transfer equation (RTE) in two-dimensional cylindrical participating media is presented. Nongray effects are treated by using a narrow-band approach. Radiative emission from CO, CO₂, H₂O, CH₄ and soot is considered. The solution procedure is applied to study radiative heat transfer in a premixed CH₄-O₂, laminar, flame. Temperature, soot and IR-active species molar fraction distributions are allowed to vary in the axial direction of the flame. From the obtained results it is possible to quantify the radiative loss in the flame, as well as the importance of soot radiation as compared to gaseous radiation. Since the solution procedure is developed for a two-dimensional cylindrical geometry, it can applied to other combustion systems such as furnaces, internal combustion engines, liquid and solid propellant combustion.

Keywords: Radiation, participating media, nongray gases, combustion

COB264 CONSTRUÇÃO E ENSAIO DE UM CORPO NEGRO PARA OPERAÇÃO A BAIXAS POTÊNCIAS TÉRMICAS / CONSTRUCTION AND TESTING OF A BLACK BODY OF LOW THERMAL POWER

Alan C.B. Rocha, George S. Marinho, Leônidas Hildebrand Jr., Renê A. Carvalho*

* Instituto de Física de São Carlos. Departamento de Engenharia Mecânica, Escola de Engenharia de São Carlos - EESC / USP. Av. Dr. Carlos Botelho, 1465- São Carlos - SP - Brasil. CEP - 13560-250.

A cavity capable of working as a black body radiator was built and tested. Whereas most comercial systems work with the cavity body fixed to the core of a heated cylinder, the new device is directly heated by means of electric resistors fixed along its external surface. The electric resistors are heated by a highly stable dc-power system, which allows the cavity to reach temperatures of the order of 250^oC. Constructed in a cone-type shape, the cavity has the back wall shaped with a large number of small pyramids, forming grooves. Its internal surface is roughly machined, forming a trap of baffles to radiation, wich leaves the cavity after multiple reflections through a unique small opening at the top of the cone. The main advantages of the system are its low cost and the simplicity of assemblying. Emissivities as high as 0.96 were measured.

Keywords: Black body, thermal cavity, emissivity, pyrometer, thermal radiation. Corpo negro, cavidade térmica, emissividade, pirômetro, radiação térmica.

COB265 DETERMINAÇÃO EXPERIMENTAL DA EMISSIVIDADE DE UM TROCADOR DE CALOR DE BAIXA POTÊNCIA TÉRMICA / EXPERIMENTAL DETERMINATION OF THE EMISSIVITY OF A LOW THERMAL POWER HEAT EXCHANGER

Alan C.B. Rocha, George S. Marinho, Leônidas Hildebrand Jr., Renê A. Carvalho*

The emissivity of a flat plate type heat exchanger was experimentally determinated by means of a compared temperature method. Two kinds of surface finishing were studied: naked aluminum, and black painted. In both situations, the plate was submited to three heating power regimes: 8.7, 24.5 and 47.9W, which correspond to surface temperatures of aproximatelly 45, 70 and 120^oC, respectivelly. The temperature distribution was measured by means of an infrared pyrometer and by thermocouples. By adjusting of the emissivity selector of the pyrometer the plate emissivity was determined.

Keywords: Emissivity, heat exchanger, natural convection, pyrometer, thermal radiation. Emissividade, trocador de calor, convecção natural, pirômetro, radiação térmica.

COB699 GERAÇÃO DE ENTROPIA EM SISTEMAS RADIANTES DE TUBOS ALETADOS/ ENTROPY GENERATION IN TUBE AND FIN RADIATING SYSTEMS

Marcio Bueno dos Santos e Sergio Mourão Saboya

Laboratório de Integração e Testes, LIT - INPE - Av. dos Astronautas, 1758 CEP 12227-010 São José dos Campos, Brasil - E-mail: bueno@lit.inpe.br

Departamento de Energia, Divisão de Engenharia Mecânica-Aeronáutica - ITA - São José dos Campos CEP 12228-900 São José dos Campos, Brasil - E-mail: saboya@mec.ita.cta.br

The entropy generation minimization method is applied to tube and fin radiative systems. The mathematical modeling of the systems lead to a non-linear integro-differential systems of equations, which is solved numerically. The entropy generation in the fin is computed. This is obtained as result of the thermal analysis of the system which gives the fin temperature distributions and the radiative heat transfer rates. Examples of optimized design are considered and discussed.

Keywords: Entropia, Irreversibilidades, Minimização, Aletas e Radiação / Entropy, Irreversibility, Minimization, Fin and Radiation.

COB811 ESTIMATION OF MONTHLY DIFFUSE SOLAR RADIATION USING ÄNGSTROM’S EQUATION LINEAR COEFFICIENT / ESTIMATIVA DA RADIAÇÃO DIFUSA MENSAL USANDO O COEFICIENTE LINEAR DA EQUAÇÃO DE ÄNGSTROM

Modesto Antonio Chaves, João Francisco Escobedo & Reinaldo Prandine Ricieri

Departamento de Ciências Ambientais, Faculdade de Ciências Agronômicas - UNESP - Botucatu - CEP 18610-000 - Botutacu, Brazil

E-Mail: modesto@surfnet.com.br

A method to estimate the diffuse solar radiation using the Änsgtrom’s equation linear coefficient is presented. The method was validated by comparison with data from the Solar Radiation Station of UNESP, Botucatu, SP, Brazil (22^o54’ South; 48⁰27’ West). Relative errors ranged from 2.71% to 29.86%, when estimated values were compared with measured data. We concluded that the method permits to estimate monthly diffuse solar radiation, with good precision, under climatic conditions in with monthly frequency of clear, partially cloudy and cloudy days is roughly the same.

Keywords: Solar Radiation - Diffuse Radiation - Radiation Modeling - Estimation of Radiation - Ängstrom’s Models

Radiação Solar - Radiação Difusa - Modelagem de Radiação - Estimativa de Radiação - Modelo de Ängstrom

COB883 MODELO DE ESTIMATIVA DAS IRRADIÂNCIAS GLOBAL E DIFUSA EM COBERTURA DE POLIETILENO / MODEL TO ESTIMATE GLOBAL AND DIFFUSE RADIATION IN POLYETHYLENE COVERAGE

Valéria de Almeida Frisina & João Francisco Escobedo

Departamento de Ciências Ambientais/FCA/UNESP/Botucatu/SP, CEP 18603-970; CP 237; TEL (014) 821 3883; FAX (014) 821 3438

This paper describes the results obtained from correlations between global and diffuse radiation inside polyethylene coverage. During 40 days, global (G) and diffuse (D) radiation were measuread outside (ex) and inside (in) polyethylene greenhouse (100 m m), for four specter conditions: open sky, partially cloudy, cloudy and the sum of the three previous conditions. The global radiation was measured with pyranometers and the diffuse radiation, with pyranometer below shadow rings. The data aquisition system consisted of a CAMPBELL 21X datalogger and a 486 DX2 microcomputer, programed to operate in 1 Hz frequence and store average of 5 minutes. The following results were obtained: Gin = 4.13 + 0.79 Gex; Din = 45.53 + 0.71 Dex. The best correlations found to the global radiation (Gin x Gex) were, in order: cloudy sky days (R² = 98.53%), open sky (R² = 96.45%) and partially cloudy sky (R² = 94.07%). The best correlations to the diffuse radiation (Din x Dex) were: cloudy sky (R² = 96.52%), open sky (R² = 78.93%) and partially cloudy sky (R² = 71.78%).

Keywords: global and diffuse radiation; polyethylene greenhouse / radiações global e difusa, estufa de polietileno

COB1187 GERACÃO DO TERMO FONTE A PARTIR DA TRANSMISSÃO DA RADIAÇÃO ÓPTICA EM TECIDOS HETEROGÊNEOS/EVALUATION OF THE HEAT SOURCE THROUGH OF THE RADIATION OPTICAL TRANSMISSION IN HETEROGENEOUS TISSUES

Paulo M. C. Gomes e Tarcísio P. R. Campos

Departamento de Engenharia Nuclear, Escola de Engenharia - UFMG

Av. do Contorno 842, 9° Andar, Centro - Belo Horizonte, MG, CEP: 30.110 - 060 E-mail: foton@cce.ufmg.br

The application of the optical spectrum on medicine has been increasing. The relevance of optical properties of laser radiation on tissues and their thermodynamic consequences are extremely important to understand and optimize surgical process. In this context, analytical and computational models for photons transport on tissue joined to the heat transport through tissue are required. A simplified model of tridimensional photons transport is proposed with the goal of setting up a methodology of photons flux calculus inside a tissue with high scattering coefficient.

Keywords: Laser, Photons Transport, Heat Transport, Finite Element, Tissue/Laser, Transporte de Fótons, transporte de Calor, Elementos Finitos, Tecido.

COB1188 GERACÃO DO TERMO FONTE A PARTIR DA TRANSMISSÃO DA RADIAÇÃO ÓPTICA EM TECIDOS HETEROGÊNEOS/EVALUATION OF THE HEAT SOURCE THROUGH OF THE RADIATION OPTICAL TRANSMISSION IN HETEROGENEOUS TISSUES

Paulo M. C. Gomes e Tarcísio P. R. Campos

Departamento de Engenharia Nuclear, Escola de Engenharia - UFMG

Av. do Contorno 842, 9° Andar, Centro - Belo Horizonte, MG, CEP: 30.110 - 060 E-mail: foton@cce.ufmg.br

Keywords: Laser, Photons Transport, Heat Transport, Finite Element, Tissue/Laser, Transporte de Fótons, transporte de Calor, Elementos Finitos, Tecido.

COB1425 ANÁLISE DO MÉTODO DE ORDENADAS DISCRETAS: DISCRETIZAÇÃO ANGULAR / ANALYSIS OF THE DISCRETE ORDINATE METHOD: ANGULAR DISCRETIZATION

Luís Mauro Moura, Dominique Baillis & Jean-François Sacadura

Institut des Sciences Appliquées de Lyon - CETHIL/TIM, ESA CNRS 5008 - 20, Av. Albert Einstein bât. 404 - 69621 Villeurbanne Cedex - France E-mail: luis@ibjfs.insa-lyon.fr - luis@lmpt.ufsc.br

This work presents a numerical analysis of different sets of quadratures involved in a discrete ordinate method used to solve the Equation of Radiative Transfer (ETR). Two different quadratures are derived from the classical Gauss and Radau ones, with the imposed condition of satisfying key half-moments of the radiative intensity. This set of quadratures are obtained through a simple translation in the Gauss or Radau full-range scheme [-1,1] to the half-range [0,1]. These quadratures are compared to cases previously analyzed by Fiveland (1985, 1987) for a slab of isotropic conservative scattering or absorbing-emitting gray medium. The results obtained with the two new set of quadratures, for the net radiative flux and the incident energy to different range of optical thicknesses and the S2, S4, S6, S8, S10, S12 ordinate sets, show a good accuracy.

Keywords: radiação térmica, ordenadas discretas, meio semitransparente, quadratura

radiative heat transfer, discrete ordinate method, semitransparent materials, quadrature

COB1427 Prediction of directional spectral emittance of an absorbing and scattering ceramic material at high temperature

Rogério Lopes; Luís Mauro Moura; Agnés Delmas & Jean-François Sacadura

Centre de Thermique de Lyon - CETHIL/TIM - 20, Avenue Albert Einstein (bât.404)

69621 Villeurbanne Cedex - France - E-mail : rogerio@ibjfs.insa-lyon.fr

Directional spectral emittance of an absorbing and scattering isotherm ceramic material (Al₂O₃) is predicted using a radiative model based on the discrete ordinates method associated to the control volume technique to solve the radiative transfer equation. The absorption (Q_a) and scattering (Q_s) efficiencies for incident radiation upon spherical particles of aluminum oxide are calculated from the Mie theory for a temperature range from 1200°C to 2020°C, the particle radius lying from 10µm to 50µm, and a range of wavelengths from 2µm to 6µm. These calculations are based on literature values of the complex index of refraction (ñ = n - ik) at high temperature for the monocrystral of sapphire (Al₂O₃). Independent scattering assumption is used. The limit of independent scattering theory is verified for a particle volume fraction ranging from 0.3 to 0.7. The spectral normal emittance of Al₂O₃ at high temperature is calculated increasing the thickness to identify the 'infinite thickness'. Calculations are performed and analyzed for different particle radius and medium temperatures.

Keywords: Emittance, semitransparent media, ceramic material, high temperature, discrete ordinates method.

COB1428 ESTUDO DE SENSIBILIDADE DE PARÂMETROS NO ACOPLAMENTO CONDUÇÃO-RADIAÇÃO/ THE SENSIVITY STUDY OF IN COUPLING CONDUCTION-RADIATION

Zaqueu Ernesto da Silva*, Michel Laurent & Dominique Ballis

*Lqboratório de Energia Solar - Ufpb e Centre de Thermique de Lyon 20, Av. Albert Einstein 69.621 - Villeurbanne - France

E-mail : dasilva@cethil.insa-lyon.fr

This paper presents the feasibility of the estimation of radiative and conductive properties from a laser flash method. A sensivity study of the coupling radiation/diffusion parameters is performed. The solid is emissive, absorbing and scattering semi-transparent. The study allows to detect the parameters that can be estimated simultaneously from the back surface temperature rise. The Levenberg-Marquardt method is used to determine the parameters.

Keywords: acoplamento, condução, radiação, método inverso, método flash/ coupling, conduction, radiation, ineverse method, flash method

COB1429 MÉTODO DAS ORDENADAS DISCRETAS ASSOCIADO A FORMA INTEGRAL DA EQUAÇÃO DE TRANSFERÊNCIA DE RADIAÇÃO EM GEOMETRIA RETANGULAR UNIDIMENSIONAL/ DISCRETE ORDINATES METHOD ASSOCIATED TO INTEGRAL FORM OF THE RADIATIVE TRANSFER EQUATION IN THE UNIDIMENSIONAL RECTANGULAR GEOMETRY

Zaqueu Ernesto da Silva*, Michel Laurent, Dominique Ballis & Severino Rodrigues de Araujo*

*Laboratório de Energia Solar - Ufpb e Centre de Thermique de Lyon 20, Av. Albert Einstein 69.621 - Villeurbanne - France

E-mail : zaqueu@les.ufpb.br

Discrete ordinates method is utilized to solve radiative transfer equation in the integral form for analysis of one-dimensional planar enclosure with absorbing, emitting, and either isotropically or anisotropically scattering medium. The main characteristic of the technical is the computing of the average intensity of the control volume. To validate the formulations, one problem test is considered and their results are compared with exact solution.

Keywords: técnica, radiação, forma integral, ordenadas discretas, retangular technique, radiation, integral form, discrete ordinates, rectangular.