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Optimum number of stages and intermediate pressure level for highest exergy efficiency in large helium liquefiers / Rijo, Jacob Thomas in International journal of refrigeration, Vol. 36 N° 8 (Décembre 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2438–2457 Titre : Optimum number of stages and intermediate pressure level for highest exergy efficiency in large helium liquefiers Titre original : Nombre d'étages et niveau de pression intermédiaire optimaux, en vue du meilleur rendement exergétique dans de grands liquéfacteurs d'hélium Type de document : texte imprimé Auteurs : Rijo, Jacob Thomas, Auteur ; Parthasarathi Ghosh, Auteur ; Kanchan Chowdhury, Auteur Année de publication : 2014 Article en page(s) : pp. 2438–2457 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Helium  liquefier;  Exergy  analysis;  Refrigeration  stages;  Expander  pressure;  Reverse  Brayton  stage;  Aspen  HYSYS Résumé : In this paper, an attempt has been made to study the influence of different design and operating parameters on the performance of large scale helium liquefiers through the concept of pre-cooling stages. Through exergy analysis and simulation with Aspen HYSYS® 7.0, it has been demonstrated that four refrigeration stages is the best option for large helium liquefiers when all expanders operate between the entire available pressure differences. However, when some of the expanders are operated at intermediate pressure, a more number of stages gives a higher thermodynamic efficiency. Relationship between the number of stages, effective heat exchanger area and operating pressure levels of expanders, which could optimally be employed for least specific power consumption has been established through exergy analysis. Optimum number of stages, intermediate pressure and corresponding plant efficiency are, however to a large extent, dictated by the prevailing compressor efficiency. The intermediate pressure that gives the maximum exergy efficiency for the plant increases from 0.2 MPa with constant compressor efficiency to 0.35 MPa when considering two-staged compressor where pressure ratio influences compressor efficiency. Results presented may be useful in designing energy-efficient helium liquefiers of large capacity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001552 [article] Optimum number of stages and intermediate pressure level for highest exergy efficiency in large helium liquefiers = Nombre d'étages et niveau de pression intermédiaire optimaux, en vue du meilleur rendement exergétique dans de grands liquéfacteurs d'hélium [texte imprimé] / Rijo, Jacob Thomas, Auteur ; Parthasarathi Ghosh, Auteur ; Kanchan Chowdhury, Auteur . - 2014 . - pp. 2438–2457. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 8 (Décembre 2013) . - pp. 2438–2457 Mots-clés : Helium  liquefier;  Exergy  analysis;  Refrigeration  stages;  Expander  pressure;  Reverse  Brayton  stage;  Aspen  HYSYS Résumé : In this paper, an attempt has been made to study the influence of different design and operating parameters on the performance of large scale helium liquefiers through the concept of pre-cooling stages. Through exergy analysis and simulation with Aspen HYSYS® 7.0, it has been demonstrated that four refrigeration stages is the best option for large helium liquefiers when all expanders operate between the entire available pressure differences. However, when some of the expanders are operated at intermediate pressure, a more number of stages gives a higher thermodynamic efficiency. Relationship between the number of stages, effective heat exchanger area and operating pressure levels of expanders, which could optimally be employed for least specific power consumption has been established through exergy analysis. Optimum number of stages, intermediate pressure and corresponding plant efficiency are, however to a large extent, dictated by the prevailing compressor efficiency. The intermediate pressure that gives the maximum exergy efficiency for the plant increases from 0.2 MPa with constant compressor efficiency to 0.35 MPa when considering two-staged compressor where pressure ratio influences compressor efficiency. Results presented may be useful in designing energy-efficient helium liquefiers of large capacity. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700713001552