Browsing by Author "Huclin, Jean Christophe"

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    Directional emissivities of semi-transparent media Cases of dihedron, infinite cylinder and cone
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Le Dez, Vital; Huclin, Jean Christophe; Lallemand, Michel
    The apparent spectral directional and hemispherical emissivities of simply shaped semi-transparent media - parallel slab, sphere, dihedron, infinite cylinder, cone - are calculated by a ray-tracing technique. The proposed method is fairly general and adapted to several geometrical coordinate systems (absolute or local) according to the nature of the surface. It includes an accurate description of the physics of the radiative transfer in presence of multi-reflections and total reflection phenomena. Calculations are worked out for the two polarizations of the radiation. A close-form expression of the directional emissivity of an infinite cylinder is given which allows validation of the general method. A mapping of the hemispherical spectral emissivities is presented for the different examined cases. These results are applied to typical silicate glasses.
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    Identification method for infrared absorption spectra of semitransparent media by their emission data Application to lime-aluminosilicate glasses at high temperatures
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Fabris, Rino; Huclin, Jean Christophe; Sakami, Mohamed; Lallemand, Michel
    The infrared absorption spectra of four Ume-aluminosihcate glasses have been studied at high temperatures in the spectral range 1 to 5 µm. The glass composition varies essentially by the FeO content. The effect of temperature is pointed out up to 1450 °C. The emission spectrometry technique used is appHed to thin slabs of semitransparent materials heated in plane-parallel platinum crucibles exposed to strong temperature gradients. The absorption coefficient is identified, for each wavelength, by a non-linear constraint optimization technique. As an illustration of the major influence of the spectrum on the heat exchanges in semitransparent devices, a modeling of the combined conductive/radiative heat transfer is performed in a glass wall.