Documents disponibles écrits par cet auteur

A general macroscopic turbulence model for flows in packed beds, channels, pipes, and rod bundles / A. Nakayama in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 10 (Octobre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 7 p. Titre : A general macroscopic turbulence model for flows in packed beds, channels, pipes, and rod bundles Type de document : texte imprimé Auteurs : A. Nakayama, Auteur ; F. Kuwahara, Auteur Année de publication : 2009 Article en page(s) : 7 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Turbulence;  kinetic  energy;  pipes;  flow  (Dynamics);  channels  (Hydraulic  engineering);  equations;  fuel  rods;  porous  materials Résumé : This study focuses on Nakayama and Kuwahara’s two-equation turbulence model and its modifications, previously proposed for flows in porous media, on the basis of the volume averaging theory. Nakayama and Kuwahara’s model is generalized so that it can be applied to most complex turbulent flows such as cross flows in banks of cylinders and packed beds, and longitudinal flows in channels, pipes, and rod bundles. For generalization, we shall reexamine the extra production terms due to the presence of the porous media, appearing in the transport equations of turbulence kinetic energy and its dissipation rate. In particular, we shall consider the mean flow kinetic energy balance within a pore, so as to seek general expressions for these additional production terms, which are valid for most kinds of porous media morphology. Thus, we establish the macroscopic turbulence model, which does not require any prior microscopic numerical experiments for the structure. Hence, for the given permeability and Forchheimer coefficient, the model can be used for analyzing most complex turbulent flow situations in homogeneous porous media without a detailed morphological information. Preliminary examination of the model made for the cases of packed bed flows and longitudinal flows through pipes and channels reveals its high versatility and performance. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...] [article] A general macroscopic turbulence model for flows in packed beds, channels, pipes, and rod bundles [texte imprimé] / A. Nakayama, Auteur ; F. Kuwahara, Auteur . - 2009 . - 7 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 7 p. Mots-clés : Turbulence;  kinetic  energy;  pipes;  flow  (Dynamics);  channels  (Hydraulic  engineering);  equations;  fuel  rods;  porous  materials Résumé : This study focuses on Nakayama and Kuwahara’s two-equation turbulence model and its modifications, previously proposed for flows in porous media, on the basis of the volume averaging theory. Nakayama and Kuwahara’s model is generalized so that it can be applied to most complex turbulent flows such as cross flows in banks of cylinders and packed beds, and longitudinal flows in channels, pipes, and rod bundles. For generalization, we shall reexamine the extra production terms due to the presence of the porous media, appearing in the transport equations of turbulence kinetic energy and its dissipation rate. In particular, we shall consider the mean flow kinetic energy balance within a pore, so as to seek general expressions for these additional production terms, which are valid for most kinds of porous media morphology. Thus, we establish the macroscopic turbulence model, which does not require any prior microscopic numerical experiments for the structure. Hence, for the given permeability and Forchheimer coefficient, the model can be used for analyzing most complex turbulent flow situations in homogeneous porous media without a detailed morphological information. Preliminary examination of the model made for the cases of packed bed flows and longitudinal flows through pipes and channels reveals its high versatility and performance. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...]

A local thermal nonequilibrium analysis of silicon carbide ceramic foam as a solar volumetric receiver / Y. Sano in Transactions of the ASME. Journal of solar energy engineering, Vol. 134 N° 2 (Mai 2012) 

Public ISBD [article]  in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 2 (Mai 2012) . - 08 p. Titre : A local thermal nonequilibrium analysis of silicon carbide ceramic foam as a solar volumetric receiver Type de document : texte imprimé Auteurs : Y. Sano, Auteur ; S. Iwase, Auteur ; A. Nakayama, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : thermal  nonequilibrium;  volumetric  solar  receiver;  popous  media:  ceramic  foam Index. décimale : 621.47 Résumé : A volumetric solar receiver receives the concentrated radiation generated by a large number of heliostats. Heat transfer takes place from the receiver solid phase to the air as it passes through the porous receiver. Such combined heat transfer within the receiver, associated radiation, convection and conduction, are investigated using a local thermal nonequilibrium model. The Rosseland approximation is applied to account for the radiative heat transfer through the solar receiver, while the low Mach approximation is exploited to investigate the compressible flow through the receiver. Analytic solutions are obtained for the developments of air and ceramic temperatures as well as the pressure along the flow direction. The results show that the pore diameter must be larger than its critical value to achieve high receiver efficiency. Subsequently, there exists an optimal pore diameter for achieving the maximum receiver efficiency under the equal pumping power. The solutions serve as a useful tool for designing a novel volumetric solar receiver of silicon carbide ceramic foam. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000002 [...] [article] A local thermal nonequilibrium analysis of silicon carbide ceramic foam as a solar volumetric receiver [texte imprimé] / Y. Sano, Auteur ; S. Iwase, Auteur ; A. Nakayama, Auteur . - 2012 . - 08 p. solar energy Langues : Anglais (eng) in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 2 (Mai 2012) . - 08 p. Mots-clés : thermal  nonequilibrium;  volumetric  solar  receiver;  popous  media:  ceramic  foam Index. décimale : 621.47 Résumé : A volumetric solar receiver receives the concentrated radiation generated by a large number of heliostats. Heat transfer takes place from the receiver solid phase to the air as it passes through the porous receiver. Such combined heat transfer within the receiver, associated radiation, convection and conduction, are investigated using a local thermal nonequilibrium model. The Rosseland approximation is applied to account for the radiative heat transfer through the solar receiver, while the low Mach approximation is exploited to investigate the compressible flow through the receiver. Analytic solutions are obtained for the developments of air and ceramic temperatures as well as the pressure along the flow direction. The results show that the pore diameter must be larger than its critical value to achieve high receiver efficiency. Subsequently, there exists an optimal pore diameter for achieving the maximum receiver efficiency under the equal pumping power. The solutions serve as a useful tool for designing a novel volumetric solar receiver of silicon carbide ceramic foam. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000002 [...]