Documents disponibles écrits par cet auteur

Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow / A.-R. A. Khaled in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Titre : Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow Type de document : texte imprimé Auteurs : A.-R. A. Khaled, Auteur ; Abdulhaiy M. Radhwan, Auteur ; S. A. Al-Muaikel, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : Laminar  falling  film  condensations;  assumptions;  accelerating  vapor  flow Résumé : Laminar falling film condensations over a vertical plate with an accelerating vapor flow is analyzed in this work in the presence of condensate suction or slip effects at the plate surface. The following assumptions are made: (i) laminar condensate flow having constant properties, (ii) pure vapor with a uniform saturation temperature in the vapor region, and (iii) the shear stress at the liquid/vapor interface is negligible. The appropriate fundamental governing partial differential equations for the condensate and vapor flows (continuity, momentum, and energy equations) for the above case are identified, nondimensionalized, and transformed using nonsimilarity transformation. The transformed equations were solved using numerical, iterative, and implicit finite-difference methods. It is shown that the freestream striking angle has insignificant influence on the condensation mass and heat transfer rates, except when slip condition is present and at relatively small Grl/Re2 values. Moreover, it is shown that increasing the values of the dimensionless suction parameter (VS) results to an increase in dimensionless mass of condensate (Γ(L)/(μl Re)) and Nusselt number (Nu(L)/Re1/2). Thus, it results in an increase in condensation mass and heat transfer rates. Finally, it is found that the condensation and heat transfer rates increase as Jakob number, slip parameter, and saturation temperature increase. Finally, the results of this work not only enrich the literature of condensation but also provide additional methods for saving thermal energy. Topics: En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of laminar falling film condensation over a vertical plate with an accelerating vapor flow [texte imprimé] / A.-R. A. Khaled, Auteur ; Abdulhaiy M. Radhwan, Auteur ; S. A. Al-Muaikel, Auteur . - 2009 . - 10 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 10 p. Mots-clés : Laminar  falling  film  condensations;  assumptions;  accelerating  vapor  flow Résumé : Laminar falling film condensations over a vertical plate with an accelerating vapor flow is analyzed in this work in the presence of condensate suction or slip effects at the plate surface. The following assumptions are made: (i) laminar condensate flow having constant properties, (ii) pure vapor with a uniform saturation temperature in the vapor region, and (iii) the shear stress at the liquid/vapor interface is negligible. The appropriate fundamental governing partial differential equations for the condensate and vapor flows (continuity, momentum, and energy equations) for the above case are identified, nondimensionalized, and transformed using nonsimilarity transformation. The transformed equations were solved using numerical, iterative, and implicit finite-difference methods. It is shown that the freestream striking angle has insignificant influence on the condensation mass and heat transfer rates, except when slip condition is present and at relatively small Grl/Re2 values. Moreover, it is shown that increasing the values of the dimensionless suction parameter (VS) results to an increase in dimensionless mass of condensate (Γ(L)/(μl Re)) and Nusselt number (Nu(L)/Re1/2). Thus, it results in an increase in condensation mass and heat transfer rates. Finally, it is found that the condensation and heat transfer rates increase as Jakob number, slip parameter, and saturation temperature increase. Finally, the results of this work not only enrich the literature of condensation but also provide additional methods for saving thermal energy. Topics: En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Investigation of heat transfer enhancement through permeable fins / A.-R. A. Khaled in Journal of heat transfer, Vol. 132 N° 3 (Mars 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 3 (Mars 2010) . - pp. [034503-1/5] Titre : Investigation of heat transfer enhancement through permeable fins Type de document : texte imprimé Auteurs : A.-R. A. Khaled, Auteur Article en page(s) : pp. [034503-1/5] Note générale : Physique Langues : Anglais (eng) Mots-clés : Conduction  Heat  transfer  Enhancement  Permeable  fins  Convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer through rectangular permeable fins is modeled and analyzed theoretically in this work. The free stream fluid flow is considered to be normal to the upper surface of the permeable fin. The flow across the permeable fin is permitted in this work. The continuity, momentum, and energy equations are solved for the fluid flow using a similarity transformation and an iterative tridiagonal finite difference method. As such, a correlation for the Nusselt number is generated as functions of the Prandtl number (Pr) and dimensionless suction velocity (fo) for 0.7 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Investigation of heat transfer enhancement through permeable fins [texte imprimé] / A.-R. A. Khaled, Auteur . - pp. [034503-1/5]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 3 (Mars 2010) . - pp. [034503-1/5] Mots-clés : Conduction  Heat  transfer  Enhancement  Permeable  fins  Convection Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer through rectangular permeable fins is modeled and analyzed theoretically in this work. The free stream fluid flow is considered to be normal to the upper surface of the permeable fin. The flow across the permeable fin is permitted in this work. The continuity, momentum, and energy equations are solved for the fluid flow using a similarity transformation and an iterative tridiagonal finite difference method. As such, a correlation for the Nusselt number is generated as functions of the Prandtl number (Pr) and dimensionless suction velocity (fo) for 0.7 DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Thermal characterizations of fin-thin film systems / A.-R. A. Khaled in Journal of heat transfer, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [104503/1-6] Titre : Thermal characterizations of fin-thin film systems Type de document : texte imprimé Auteurs : A.-R. A. Khaled, Auteur Année de publication : 2010 Article en page(s) : pp. [104503/1-6] Note générale : Physique Langues : Anglais (eng) Mots-clés : Conduction  Convection  Fins  Enhancements  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : This work considers heat transfer in fin-thin film systems. Two types of these systems are analyzed: (A) a thin film sandwiched between two identical fin halves, and (B) a fin sandwiched between two identical thin films. The corresponding coupled energy equations are solved numerically by an implicit, iterative, finite-difference scheme. Comparisons with derived approximate closed-form solutions are performed and good agreement is obtained. A parametric study of all involved parameters is conducted and presented graphically. Useful correlations containing the various physical parameters for both types are reported. It is found that thermal efficiencies of fins can be increased significantly by introducing an internal flow inside the fin material. Moreover, factors producing more internal convections are found to increase the fin-thin film thermal efficiency. In addition, thermal efficiencies of type A systems are found to be higher than those of type B systems. Moreover, the resulting system thermal efficiency is found to have at most one local maximum and one local minimum over the whole relative heights ratio spectrum. Finally, this work paves a way for an effective combined passive and active method for enhancing heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Thermal characterizations of fin-thin film systems [texte imprimé] / A.-R. A. Khaled, Auteur . - 2010 . - pp. [104503/1-6]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [104503/1-6] Mots-clés : Conduction  Convection  Fins  Enhancements  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : This work considers heat transfer in fin-thin film systems. Two types of these systems are analyzed: (A) a thin film sandwiched between two identical fin halves, and (B) a fin sandwiched between two identical thin films. The corresponding coupled energy equations are solved numerically by an implicit, iterative, finite-difference scheme. Comparisons with derived approximate closed-form solutions are performed and good agreement is obtained. A parametric study of all involved parameters is conducted and presented graphically. Useful correlations containing the various physical parameters for both types are reported. It is found that thermal efficiencies of fins can be increased significantly by introducing an internal flow inside the fin material. Moreover, factors producing more internal convections are found to increase the fin-thin film thermal efficiency. In addition, thermal efficiencies of type A systems are found to be higher than those of type B systems. Moreover, the resulting system thermal efficiency is found to have at most one local maximum and one local minimum over the whole relative heights ratio spectrum. Finally, this work paves a way for an effective combined passive and active method for enhancing heat transfer. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]