Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials : Hastelloy X, Haynes 230, and Alloy 617

Maynard, Raymond K.

doi:10.32469/10355/14216

Cited by 4 publications

(9 citation statements)

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“…In the step two characteristic of standard calibration procedures, complex emissivity tests [8][9][10][11][12][13][14][15][16] have to be conducted in order to calculate the correction factor for (Eq. 7) needed to obtain the real surface temperature ( in Eq.…”

Section: A) Basmentioning

confidence: 99%

Design of the Experimental Campaign on Variable Transpiration Cooling for Reusable Thermal Protection Systems

Gulli¹,

Maddalena²,

Moghadam

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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Reusable thermal protection systems are one of the key technologies that have to be improved in order to enable long-duration hypersonic flights and a more affordable access-to-space by means of single-stage-toorbit vehicles. The transpiration cooling has been demonstrated to be one of the most promising cooling techniques in terms of coolant mass saving and minimum disturbances of the external flow. The coupling of the boundary layer with the thermal response of selected porous materials plays a crucial role in enabling the practical use of the transpiration cooling technique for reusable thermal protection systems. Numerical studies conducted by the authors, on the aforementioned coupling, have introduced the new concept of the variable transpiration cooling which allowed identifying a particular cooling strategy (i.e. saw-tooth wall velocity distribution) able to reduce the total amount of coolant used by 37% with respect to other cooling strategies explored. The current capability of manipulating the natural properties of porous materials (e.g. porosity, permeability and thermal conductivity) renewed the interest on demonstrating experimentally the cooling potential of the transpiration strategies simulated numerically. The design phase of the experimental campaign on variable transpiration cooling for testing a full-scale thermal protection system in the 1.6 MW arc-heated wind tunnel located at the University of Texas at Arlington is presented in this work. The prototype thermal shield to be used for the experiments is an axisymmetric carbon-carbon cone having tailored porosity and variable thickness prescribed at the manufacturing level in order to reproduce a variable blowing profile. An innovative calibration procedure of the infrared camera used to map the temperature of the external surface, which is based on simultaneous measurements of the local temperature and intensity of radiation, is described in detail. The results obtained in this work highlight the potential of using the calibration methodology proposed for retrieving the surface temperatures without using blackbody radiators/cavities and without relying on elaborated tests for emissivity characterization which are both needed in standard calibration procedures for infrared camera systems. A preliminary analysis of the optical properties of the plasma flow is also provided in order to assess the impact of the plasma's emissivity on the surface temperature map that will be obtained during the final experiment on transpiration cooling.

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Section: A) Basmentioning

confidence: 99%

Design of the Experimental Campaign on Variable Transpiration Cooling for Reusable Thermal Protection Systems

Gulli¹,

Maddalena²,

Moghadam

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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“…The temperature is free of any measurement error (i.e., e =0). Three commonly-used turbine blade fin materials based on the values of k a ,  and  are analyzed, the values of which have been obtained from available sources [35][36][37][38][39][40]. It is worth to mention that the surface emissivity also depends on the surface roughness [40].…”

Section: Let Us Considermentioning

confidence: 99%

Predicting Dimensions of a Rectangular Fin Satisfying a Given Internal Heat Generation Using Inverse Method

Das

2015

ASME 2015 Gas Turbine India Conference

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This paper deals with a computational study to predict important dimensions of a rectangular fin used in gas turbine blade cooling for satisfying a prescribed internal heat generation. The heat transfer is assumed to occur by simultaneous conduction, convection and radiation. The effect of temperature-dependent thermal conductivity has been also taken into consideration. Rectangular fin geometry has been considered due to its simplicity and easiness of fabrication. Corresponding to known values of various thermo-physical parameters, at first using the fourth order implicit Runge-Kutta-based forward method, the relevant steady-state temperature distribution is evaluated. Forward method has been well-validated with three numerical schemes and experimental data. Thereafter, an inverse problem is solved using the genetic algorithm (GA) for predicting fin dimensions satisfying a prescribed temperature distribution corresponding to a fixed internal heat generation. The relevant objective function has been formulated using a three-point error minimization technique represented by square of residuals between guessed and available temperature distributions. The analysis has been done for three different fin materials such as Inconel, Hastelloy and Titanium. These materials are generally used in gas turbine blade applications due to their high melting point along with good fatigue, corrosion and creep properties. Effects of random measurement errors following a Gaussian profile are analyzed. The variations of relevant parameters are studied at different generations of GA. It is observed that for a given fin material, many feasible dimensions can sustain a given amount of internal heat generation which offer sufficient scopes to the fin designer. For the required amount of heat generation, the suitability of estimated parameters has been verified by the comparison between actual and reconstructed temperature distributions alongwith minimization of total fin volume. The present work is proposed to be useful in selecting appropriate dimensional fin configurations corresponding to a given material which can satisfy a fixed amount of internal heat generation.

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“…Nas medições utilizando sensores infravermelhos, a intensidade da radiação emitida por uma superfície atravessa o meio até o elemento sensor do instrumento. Portanto, possibilitando que a radiação emitida seja somada à radiação do raio próximo, a reflexões e a possíveis interferências provocadas por fenômenos diversos (FU et al, 2012;MAYNARD, 2011). Para evitar isso, as leituras de temperatura feitas por meio de sistemas de medição infravermelhos devem ser realizadas com a menor distância possível entre sensor e objeto medido, minimizando interferências decorrentes de efeitos provocados por fatores externos.…”

Section: Método Radiométricounclassified

“…As perdas de energia Qcond e • ""2' , ao longo do comprimento da barra de SMA, são insignificantes, em comparação com a perda de calor por radiação (MAYNARD, 2011). A energia que deixa a superfície sob a forma de calor por radiação Q˜™ š devido à diferença de temperatura entre SMA e o meio ambiente pode ser expressa por: No vácuo e em estado estacionário, a potência elétrica fornecida para o aquecimento da barra de SMA é aproximadamente igual a dissipação de calor a partir da superfície do CP por radiação.…”

Section: Linha Da Bombaunclassified

“…Nos metais a emissão de radiação térmica pode ser analisada como um fenômeno de superfície, portanto, o desconhecimento da emissividade superficial pode restringir a aplicação ou comprometer a confiabilidade do método (HERVE, et al, 2012). Estudos comprovam que a emissividade é influenciada pelas condições de superfície, por exemplo, rugosidade e oxidação, podendo ser específica para temperatura e banda do espectro infravermelho (MAYNARD, 2011). Nas ligas com memória de forma a rugosidade varia com a temperatura devido à transformação de fase que o material sofre quando submetido a determinadas temperaturas (SUTAPUN et al, 1998;HUANG e ZHANG, 2002).…”

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Concepção, projeto, construção e testes de um aparato experimental para medição de emissividade de ligas com memória de forma

Silva¹

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Agradeço primeiramente a Deus, pela minha vida, aos meus pais (Cosme e Rosa) por todo incentivo e por mobilizar-se em prol da melhoria de minha vida, ao longo desses anos longe de casa. Agradeço aos professores do curso dePós-Graduação em Sistemas Mecatrônicos da UnB, em especial ao meu orientador, professor Edson Paulo da Silva, por inúmeras sugestões, incentivos e principalmente por assumir o desafio de orientar-me no que se refere ao desenvolvimento deste trabalho experimental, até então pouco explorado no âmbito acadêmico. Agradeço ao aluno do curso de Engenharia Mecatrônica da UnB, Thiago Barra, que esteve comigo durante o desenvolvimento deste trabalho, compartilhando conhecimentos e dificuldades. E a todos os técnicos do

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Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials : Hastelloy X, Haynes 230, and Alloy 617

Cited by 4 publications

References 0 publications

Design of the Experimental Campaign on Variable Transpiration Cooling for Reusable Thermal Protection Systems

Design of the Experimental Campaign on Variable Transpiration Cooling for Reusable Thermal Protection Systems

Predicting Dimensions of a Rectangular Fin Satisfying a Given Internal Heat Generation Using Inverse Method

Concepção, projeto, construção e testes de um aparato experimental para medição de emissividade de ligas com memória de forma

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