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Détermination des paramètres radiatifs d'un isolant fibreux : théorie de Mie, oscillateurs de Lorentz et méthode inverse

Abstract : This work is devoted to the study of the radiative properties of fibrous media formed by silica fibre. The determination of these properties is essential in order to make a modelisation of thermal transfer. Two approaches are used to characterise the media. A first approach is a method based on the study of the interaction between matter and radiation using the MIE theory. The model obtained depends only on optical parameters (indices of silica) and on morphological parameters (diameter and orientation of fibres, density of the medium). Simulations make it possible to insist on the strongly anisotropie behaviour of the scattering of the radiation by a fibre and to study the influence of various parameters on the radiative properties of the medium. The use of the model of LORENTZ oscillators enables to establish the link between the modes of vibration within the silica and the properties of the medium with respect to the radiation. The results of the MIE theory make possible the simulation of the heat transfer coupled by radiation and conduction. The second approach is an inverse method based on experimental measurements of bidirectional reflection and transmission. Silica wool and fabric samples are studied by using an apparatus formed by goniometric device and a monochromator with gratings. The inverse method allows, by the means of a model of least squares, the determination of the radiative properties of the medium: albedo, optical thickness and coefficients of the phase function. A new model of phase function taking into account HENYEY and GREENSTEIN functions associated with a LORENTZ function is used. Our results achieved with the inverse method are close to those obtained by the MIE theory. The variations come from the heterogeneity of the medium, the experimental protocol and the necessarily simple model to identify a reduced number of parameters in inverse method.
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Submitted on : Thursday, March 29, 2018 - 10:41:11 AM
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Arnaud Milandri. Détermination des paramètres radiatifs d'un isolant fibreux : théorie de Mie, oscillateurs de Lorentz et méthode inverse. Autre. Université Henri Poincaré - Nancy 1, 2000. Français. ⟨NNT : 2000NAN10187⟩. ⟨tel-01746607⟩



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