CABRERA SÁNCHEZ, AGUSTÍN Y FAMILIA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Identification optimale des propriétés thermophysiques d’un revêtement

International audienceThe inverse problem of simultaneous estimation of diffusivity and effusivity of a coating is solved. It deals with: the experiment definition (pulsed photothermal method), the developpement of the corresponding parametrized direct model, the minimisation of the ordinary least squares objective function and the analysis of confidence of the estimated parameters. The optimal design of experiment, based on the analysis of the sensitivity coefficients of the direct model, enables to limit the noise amplification during inversion. Such a methodology has made a coating caracterisation possible, even if its thermophysical properties were close to those of Us substrate (chromium/steel).Le problème inverse d’identification simultanée de la diffusivité et de l’effusivité d’un revêtement est résolu. Il intègre : la définition de l’expérience (méthode photothermique impulsionnelle), le développement de son modèle direct paramétré, la minimisation du critère des moindres carrés ordinaires entre mesure et modèle et enfin l’analyse des incertitudes sur les paramètres modèles estimés. La conception de l’expérience optimale, basée sur l’étude des coefficients de sensibilité du modèle, permet de limiter l’amplification du bruit de mesure lors de l’inversion. Une telle démarche a permis de caractériser un revêtement dont les propriétés thermophysiques sont voisines de celles de son substrat (chrome/acier)

An experimental identification of line heat sources in a diffusive system using the boundary element method

International audienceThis paper deals with an inverse problem which consists of the experimental identification of line heat source strength in an homogeneous solid using temperature measurements. An inverse formulation using the boundary element method, is used to identify the strength of line heat sources. In the case of multiple sources identification the location is assumed to be known but, in the case of a single source, an iterative algorithm for the location identification is proposed. The experiment consists of the identi®cation of the power dissipated by Joule effect in one or two thin wires placed in a long square section cement bar. The measurements necessary to solve the inverse problem are provided by thermocouples for the internal temperatures and by infrared thermography for the superficial temperatures. A time regularization procedure associated to future time steps is used to correctly solve the ill-posed problem

Pressure drop in metallic foam : emphasis on flow laws experimental determination

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Lecture 2 : Basics for linear estimation, the white box case

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Effective Emissivity Measurements of Powders and Their Mixtures

International audienceIn this paper, an experimental measurement technique of the effective emissivity of powders is presented for a given spectral field, using the reflectance hemisphere method. This technique consists of heating a powder filled into a Teflon (r) cell, through a thin copper layer. The apparent temperature of the powder surface is then measured by an infrared camera, either directly or through an orifice arranged into the hemisphere. The effective emissivity is identified by comparing the flux emitted by the powder surface and that emitted by a specular hemisphere taken as a reference blackbody, for the same temperature and the same spectral wavelength field. The results are presented for a metallic and an insulating powder, and validated with literature values. The effective emissivities of powder mixtures are also presented in this paper

Highly Porous Metal Foams: Effective Thermal Conductivity Measurement Using a Photothermal Technique

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Lecture 2 : Basics for linear estimation, the white box case

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Use of a pseudo-random heating excitation to investigate the thermal properties of thermally fragile materials

International audienceIn this numerical study, a photothermal method with random excitation is implemented in order to measure the thermal diffusivity of thermally fragile materials. The principle of this technique is based on rebuilding the sample impulse response through input-output cross-correlatoin. A D-optimality criterion is used to determine the optimal duration of the experiment. The thermophysical properties are identified through the rebuilt impulse response using an iterative method which minimizes the gap between simulated measurements and theoretical temperature calculated using the thermal quadripoles method. The obtained results show a good agreement with literature values