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Effect of rib spacing on heat transfer in a two pass rectangular channel (AR = 2:1) at high rotation numbers / Lei Jiang in Journal of heat transfer, Vol 134 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 09 p. Titre : Effect of rib spacing on heat transfer in a two pass rectangular channel (AR = 2:1) at high rotation numbers Type de document : texte imprimé Auteurs : Lei Jiang, Auteur ; Je-Chin Han, Auteur ; Michael Huh, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : gas  turbine  heat  transfer;  forced  convection;  heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this paper, the effect of rib spacing on heat transfer in a rotating two-passage channel (aspect ratio, AR = 2:1) at orientation angle of 135 deg was studied. Parallel ribs were applied' on leading and trailing walls of the rotating channel at the flow angle of 45 deg. The rib-height-to-hydraulic diameter ratio (e/Dh) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000, and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under nonrotation conditions. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Correlations of Nusselt number ratio (Nu/Nus) to rotation number (Ro) or local buoyancy parameter (Box) are existent on all surfaces (leading, trailing, inner and outer walls, and tip cap region) in the two-passage 2:1 aspect ratio channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...] [article] Effect of rib spacing on heat transfer in a two pass rectangular channel (AR = 2:1) at high rotation numbers [texte imprimé] / Lei Jiang, Auteur ; Je-Chin Han, Auteur ; Michael Huh, Auteur . - 2012 . - 09 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol 134 N° 9 (Septembre 2012) . - 09 p. Mots-clés : gas  turbine  heat  transfer;  forced  convection;  heat  transfer  enhancement Index. décimale : 536 Chaleur. Thermodynamique Résumé : In this paper, the effect of rib spacing on heat transfer in a rotating two-passage channel (aspect ratio, AR = 2:1) at orientation angle of 135 deg was studied. Parallel ribs were applied' on leading and trailing walls of the rotating channel at the flow angle of 45 deg. The rib-height-to-hydraulic diameter ratio (e/Dh) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000, and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under nonrotation conditions. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Correlations of Nusselt number ratio (Nu/Nus) to rotation number (Ro) or local buoyancy parameter (Box) are existent on all surfaces (leading, trailing, inner and outer walls, and tip cap region) in the two-passage 2:1 aspect ratio channel. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000009 [...]

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 [...]

High rotation number effect on heat transfer in a triangular channel with 45 deg, inverted 45 deg, and 90 deg ribs / Yao-Hsien Liu in Journal of heat transfer, Vol. 132 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 7 (Juillet 2010) . - pp. [071702-1/10] Titre : High rotation number effect on heat transfer in a triangular channel with 45 deg, inverted 45 deg, and 90 deg ribs Type de document : texte imprimé Auteurs : Yao-Hsien Liu, Auteur ; Michael Huh, Auteur ; Je-Chin Han, Auteur Article en page(s) : pp. [071702-1/10] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat  transfer  Turbulence  promoter  Triangular  channel  High  rotation  number Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer and pressure drop have been experimentally investigated in an equilateral triangular channel (Dh=1.83 cm), which can be used to simulate the internal cooling passage near the leading edge of a gas turbine blade. Three different rib configurations (45 deg, inverted 45 deg, and 90 deg) were tested at four different Reynolds numbers (10,000–40,000), each with five different rotational speeds (0–400 rpm). The rib pitch-to-height (P/e) ratio is 8 and the height-to-hydraulic diameter (e/Dh) ratio is 0.087 for every rib configuration. The rotation number and buoyancy parameter achieved in this study were 0–0.58 and 0–2.3, respectively. Both the rotation number and buoyancy parameter have been correlated with predict the rotational heat transfer in the ribbed equilateral triangular channel. For the stationary condition, staggered 45 deg angled ribs show the highest heat transfer enhancement. However, staggered 45 deg angled ribs and 90 deg ribs have the higher comparable heat transfer enhancement at rotating condition near the blade leading edge region. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] High rotation number effect on heat transfer in a triangular channel with 45 deg, inverted 45 deg, and 90 deg ribs [texte imprimé] / Yao-Hsien Liu, Auteur ; Michael Huh, Auteur ; Je-Chin Han, Auteur . - pp. [071702-1/10]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 7 (Juillet 2010) . - pp. [071702-1/10] Mots-clés : Heat  transfer  Turbulence  promoter  Triangular  channel  High  rotation  number Index. décimale : 536 Chaleur. Thermodynamique Résumé : Heat transfer and pressure drop have been experimentally investigated in an equilateral triangular channel (Dh=1.83 cm), which can be used to simulate the internal cooling passage near the leading edge of a gas turbine blade. Three different rib configurations (45 deg, inverted 45 deg, and 90 deg) were tested at four different Reynolds numbers (10,000–40,000), each with five different rotational speeds (0–400 rpm). The rib pitch-to-height (P/e) ratio is 8 and the height-to-hydraulic diameter (e/Dh) ratio is 0.087 for every rib configuration. The rotation number and buoyancy parameter achieved in this study were 0–0.58 and 0–2.3, respectively. Both the rotation number and buoyancy parameter have been correlated with predict the rotational heat transfer in the ribbed equilateral triangular channel. For the stationary condition, staggered 45 deg angled ribs show the highest heat transfer enhancement. However, staggered 45 deg angled ribs and 90 deg ribs have the higher comparable heat transfer enhancement at rotating condition near the blade leading edge region. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

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 [...]