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Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers / Nawaf Y. Alkhamis in Journal of heat transfer, Vol. 133 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111901/1-8] Titre : Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers Type de document : texte imprimé Auteurs : Nawaf Y. Alkhamis, Auteur ; Akhilesh P. Rallabandi, Auteur ; Je-Chin Han, Auteur Année de publication : 2012 Article en page(s) : pp. [111901/1-8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Rib  turbulators  Internal  coolings  Gas  turbine  cooling  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...] [article] Heat transfer and pressure drop correlations for square channels with V-shaped ribs at high Reynolds numbers [texte imprimé] / Nawaf Y. Alkhamis, Auteur ; Akhilesh P. Rallabandi, Auteur ; Je-Chin Han, Auteur . - 2012 . - pp. [111901/1-8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 11 (Novembre 2011) . - pp. [111901/1-8] Mots-clés : Rib  turbulators  Internal  coolings  Gas  turbine  cooling  Heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+). DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000133000011 [...]

Unsteady wake and coolant density effects on turbine blade film cooling using pressure sensitive paint technique / Akhilesh P. Rallabandi in Journal of heat transfer, Vol. 134 N° 8 (special issue) (Août 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 8 (special issue) (Août 2012) . - 10 p. Titre : Unsteady wake and coolant density effects on turbine blade film cooling using pressure sensitive paint technique Type de document : texte imprimé Auteurs : Akhilesh P. Rallabandi, Auteur ; Shiou-Jiuan Li, Auteur ; Je-Chin Han, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : unsteady  wake;  film-cooling  effectiveness;  pressure  sensitive  paint Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effect of an unsteady stator wake (simulated by wake rods mounted on a spoke-wheel wake generator) on the modeled rotor blade is studied using the pressure sensitive paint (PSP) mass-transfer analogy method. Emphasis of the current study is on the midspan region of the blade. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blade also has radial shower-head leading edge film-cooling holes. Strouhal numbers studied range from 0 to 0.36; the exit Reynolds number based on the axial chord is 530,000. Blowing ratios range from 0.5 to 2.0 on the suction side and 0.5 to 4.0 on the pressure side. Density ratios studied range from 1.0 to 2.5, to simulate actual engine conditions. The convex suction surface experiences film-cooling jet lift-off at higher blowing ratios, resulting in low effectiveness values. The film coolant is found to reattach downstream on the concave pressure surface, increasing effectiveness at higher blowing ratios. Results show deterioration in film-cooling effectiveness due to increased local turbulence caused by the unsteady wake, especially on the suction side. Results also show a monotonic increase in film-cooling effectiveness on increasing the coolant to mainstream density ratio. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000008 [...] [article] Unsteady wake and coolant density effects on turbine blade film cooling using pressure sensitive paint technique [texte imprimé] / Akhilesh P. Rallabandi, Auteur ; Shiou-Jiuan Li, Auteur ; Je-Chin Han, Auteur . - 2012 . - 10 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 8 (special issue) (Août 2012) . - 10 p. Mots-clés : unsteady  wake;  film-cooling  effectiveness;  pressure  sensitive  paint Index. décimale : 536 Chaleur. Thermodynamique Résumé : The effect of an unsteady stator wake (simulated by wake rods mounted on a spoke-wheel wake generator) on the modeled rotor blade is studied using the pressure sensitive paint (PSP) mass-transfer analogy method. Emphasis of the current study is on the midspan region of the blade. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blade also has radial shower-head leading edge film-cooling holes. Strouhal numbers studied range from 0 to 0.36; the exit Reynolds number based on the axial chord is 530,000. Blowing ratios range from 0.5 to 2.0 on the suction side and 0.5 to 4.0 on the pressure side. Density ratios studied range from 1.0 to 2.5, to simulate actual engine conditions. The convex suction surface experiences film-cooling jet lift-off at higher blowing ratios, resulting in low effectiveness values. The film coolant is found to reattach downstream on the concave pressure surface, increasing effectiveness at higher blowing ratios. Results show deterioration in film-cooling effectiveness due to increased local turbulence caused by the unsteady wake, especially on the suction side. Results also show a monotonic increase in film-cooling effectiveness on increasing the coolant to mainstream density ratio. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000008 [...]