Emissivity of high-temperature fiber composites / Xiangning Li in Industrial & engineering chemistry research, Vol. 48 N°4 (Février 2009)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - p. 2236–2244 Titre : Emissivity of high-temperature fiber composites Type de document : texte imprimé Auteurs : Xiangning Li, Auteur ; William Strieder, Auteur Année de publication : 2009 Article en page(s) : p. 2236–2244 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : High-temperature fiber composites Edge surface Résumé : Effective emissivities of high-temperature fiber composites are calculated for several external edge surface structures—randomly overlapping, parallel cylinders of radius a protruding out a distance δ from the composite matrix, with central axes either perpendicular to or into the direction of the composite external edge. First-order multiple scattering reciprocal bounds provide effective emissivity values, usually within an error of 10% or less; e.g., for carbon−carbon composites with a fiber−matrix emissivity of εs = 0.8 and a fiber fraction of 30 vol %, the maximum error bound is 4%−5%. The fundamental behavior of the effective emissivity, as a function of protrusion depth, is examined, and significant deep-bed, blackbody radiative effects are observed, even at modest model protrusions. A maximum value for the fiber composite effective emissivity at an optimum porosity is found for any given ratio of protrusion length to fiber radius (δ/a) and fiber−matrix emissivity (εs); e.g., for a perpendicular protrusion with δ/a = 3 and εs = 0.5, a maximum effective emissivity enhancement of 27% is found at Φ = 0.6, and for fibers protruding parallel to the edge with δ/a = 3 and εs = 0.5, a maximum enhancement of 21% is observed at Φ = 0.6. Model equation results agree with the measured effective emissivity values of carbon−carbon brake composites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008583 [article] Emissivity of high-temperature fiber composites [texte imprimé] / Xiangning Li, Auteur ; William Strieder, Auteur . - 2009 . - p. 2236–2244. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - p. 2236–2244 Mots-clés : High-temperature fiber composites Edge surface Résumé : Effective emissivities of high-temperature fiber composites are calculated for several external edge surface structures—randomly overlapping, parallel cylinders of radius a protruding out a distance δ from the composite matrix, with central axes either perpendicular to or into the direction of the composite external edge. First-order multiple scattering reciprocal bounds provide effective emissivity values, usually within an error of 10% or less; e.g., for carbon−carbon composites with a fiber−matrix emissivity of εs = 0.8 and a fiber fraction of 30 vol %, the maximum error bound is 4%−5%. The fundamental behavior of the effective emissivity, as a function of protrusion depth, is examined, and significant deep-bed, blackbody radiative effects are observed, even at modest model protrusions. A maximum value for the fiber composite effective emissivity at an optimum porosity is found for any given ratio of protrusion length to fiber radius (δ/a) and fiber−matrix emissivity (εs); e.g., for a perpendicular protrusion with δ/a = 3 and εs = 0.5, a maximum effective emissivity enhancement of 27% is found at Φ = 0.6, and for fibers protruding parallel to the edge with δ/a = 3 and εs = 0.5, a maximum enhancement of 21% is observed at Φ = 0.6. Model equation results agree with the measured effective emissivity values of carbon−carbon brake composites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008583

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