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Experimental investigation of flow field structure in mixing tee / Seyed Mohammad Hosseini in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 5 (Mai 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 5 (Mai 2009) . - 07 p. Titre : Experimental investigation of flow field structure in mixing tee Type de document : texte imprimé Auteurs : Seyed Mohammad Hosseini, Auteur ; Kazuhisa Yuki, Auteur ; Hidetoshi Hashizume, Auteur Année de publication : 2009 Article en page(s) : 07 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : T-junction;  cooling  system;  turbulent  flow Résumé : T-junction is one of the familiar components in the cooling system of power plants with enormous capability of high-cycle thermal fatigue. This research investigates the structure and mixing mechanism of turbulent flow in a T-junction area with a 90 deg bend upstream. According to the wide distribution of turbulent jets in the T-junction, a re-attached jet was selected previously as the best representative condition with the highest velocity fluctuation and the most complex structure. For considering the mixing mechanism of re-attached jet, T-junction is subdivided into few lateral and longitudinal sections, and each section is visualized separately by particle image velocimetry technique. Corresponding to the experimental data, the branch flow acts as a finite turbulent jet, develops the alternative type of eddies, and causes the high velocity fluctuation near the main pipe wall. Three regions are mainly subject to maximum velocity fluctuation: the region close to the jet boundaries (fluctuation mostly is caused by Kelvin–Helmholtz instability), the region above the jet and along the main flow (fluctuation mostly is caused by Karman vortex), and the re-attached area (fluctuation mostly is caused by changing the pressure gradient in the wake area above the jet). Finally, the re-attached area (near the downstream of wake area above the jet) is introduced as a region with strongest possibility to high-cycle thermal fatigue with most effective velocity fluctuation on the main pipe wall above the branch nozzle. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Experimental investigation of flow field structure in mixing tee [texte imprimé] / Seyed Mohammad Hosseini, Auteur ; Kazuhisa Yuki, Auteur ; Hidetoshi Hashizume, Auteur . - 2009 . - 07 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 5 (Mai 2009) . - 07 p. Mots-clés : T-junction;  cooling  system;  turbulent  flow Résumé : T-junction is one of the familiar components in the cooling system of power plants with enormous capability of high-cycle thermal fatigue. This research investigates the structure and mixing mechanism of turbulent flow in a T-junction area with a 90 deg bend upstream. According to the wide distribution of turbulent jets in the T-junction, a re-attached jet was selected previously as the best representative condition with the highest velocity fluctuation and the most complex structure. For considering the mixing mechanism of re-attached jet, T-junction is subdivided into few lateral and longitudinal sections, and each section is visualized separately by particle image velocimetry technique. Corresponding to the experimental data, the branch flow acts as a finite turbulent jet, develops the alternative type of eddies, and causes the high velocity fluctuation near the main pipe wall. Three regions are mainly subject to maximum velocity fluctuation: the region close to the jet boundaries (fluctuation mostly is caused by Kelvin–Helmholtz instability), the region above the jet and along the main flow (fluctuation mostly is caused by Karman vortex), and the re-attached area (fluctuation mostly is caused by changing the pressure gradient in the wake area above the jet). Finally, the re-attached area (near the downstream of wake area above the jet) is introduced as a region with strongest possibility to high-cycle thermal fatigue with most effective velocity fluctuation on the main pipe wall above the branch nozzle. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Long-term deactivation of a commercial CoMo/γ-Al2O3 catalyst in hydrodesulfurization of a naphtha stream / Morteza Baghalha in Industrial & engineering chemistry research, Vol. 48 N° 7 (Avril 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 7 (Avril 2009) . - pp. 3331–3340 Titre : Long-term deactivation of a commercial CoMo/γ-Al2O3 catalyst in hydrodesulfurization of a naphtha stream Type de document : texte imprimé Auteurs : Morteza Baghalha, Auteur ; Seyed Mohammad Hosseini, Auteur Année de publication : 2009 Article en page(s) : pp. 3331–3340 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : CoMo/γ-Al2O3  catalyst  Naphtha  stream  Hydrodesulfurization  Fixed  bed  reactor Résumé : Long-term deactivation of a commercial CoMo/γ-Al2O3 catalyst used in the hydrodesulfurization of a naphtha stream was studied using 35 months of operating data of an industrial HDS fixed bed reactor. The major sulfur-containing species of the naphtha feed was identified as 2-ethyl-4-methylthiophene (2E4MT) based on GC-MS analysis. The characterization of the industrial catalysts was performed by BET, XRD, XRF, and HCN Leco analyses. The reaction rate constant of the gas-phase hydrodesulfurization reaction was calculated by fitting the industrial reactor conversion data to the Hougen−Watson rate equation, assuming that the surface reaction between the sulfur-containing species and adsorbed hydrogen is the rate-determining step. The effectiveness factor was ∼0.91, nearly constant along the catalyst bed, implicitly implying that the HDS reaction is approximately first order in 2E4MT concentration. From the combined kinetics and characterization analyses, it was found that the main mechanisms of deactivation of the commercial HDS catalysts were (1) sulfur loss and coke deposition (recoverable by regeneration) and (2) Co−Mo−S permanent loss of activity. After 7 months of operation (before the first regeneration), the share of each deactivation mechanism in the loss of activity is (1) 81% and (2) 19%. The Co−Mo−S permanent loss of activity is assumed to be caused by arsenic poisoning, Co reaction with the alumina matrix, and decrease in the catalytic active surface area. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801743v [article] Long-term deactivation of a commercial CoMo/γ-Al2O3 catalyst in hydrodesulfurization of a naphtha stream [texte imprimé] / Morteza Baghalha, Auteur ; Seyed Mohammad Hosseini, Auteur . - 2009 . - pp. 3331–3340. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 7 (Avril 2009) . - pp. 3331–3340 Mots-clés : CoMo/γ-Al2O3  catalyst  Naphtha  stream  Hydrodesulfurization  Fixed  bed  reactor Résumé : Long-term deactivation of a commercial CoMo/γ-Al2O3 catalyst used in the hydrodesulfurization of a naphtha stream was studied using 35 months of operating data of an industrial HDS fixed bed reactor. The major sulfur-containing species of the naphtha feed was identified as 2-ethyl-4-methylthiophene (2E4MT) based on GC-MS analysis. The characterization of the industrial catalysts was performed by BET, XRD, XRF, and HCN Leco analyses. The reaction rate constant of the gas-phase hydrodesulfurization reaction was calculated by fitting the industrial reactor conversion data to the Hougen−Watson rate equation, assuming that the surface reaction between the sulfur-containing species and adsorbed hydrogen is the rate-determining step. The effectiveness factor was ∼0.91, nearly constant along the catalyst bed, implicitly implying that the HDS reaction is approximately first order in 2E4MT concentration. From the combined kinetics and characterization analyses, it was found that the main mechanisms of deactivation of the commercial HDS catalysts were (1) sulfur loss and coke deposition (recoverable by regeneration) and (2) Co−Mo−S permanent loss of activity. After 7 months of operation (before the first regeneration), the share of each deactivation mechanism in the loss of activity is (1) 81% and (2) 19%. The Co−Mo−S permanent loss of activity is assumed to be caused by arsenic poisoning, Co reaction with the alumina matrix, and decrease in the catalytic active surface area. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801743v