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Transfert de chaleur et configuration de l'écoulement en ébullition du CO2 dans des minicanaux.

Heat transfer and flow pattern of boiling flow CO2 in minichannels.

Auteurs : HARA T., UMEKAWA H., OZAWA M., et al.

Résumé

Increasing attention has been given to carbon dioxide as an alternative refrigerant in refrigeration and air conditioning from a framework of global environment, such as ozone depletion and global warming. The boiling heat transfer of carbon dioxide is thus a key parameter in designing the heat exchangers with a small-bore tube. This paper describes the flow patterns observed in horizontal mini-channels ranging from 0.51 to 3.0 mm in diameter, together with the flow pattern maps and related boiling heat transfer characteristics, of carbon dioxide in a wide range of pressure. The test section was horizontal round tubes having Joule heating of AC power. The operating pressure was in the range around 4 to 7 MPa, the mass flux covered 80 to 700 kg/m2.s.The observed flow patterns are mainly classified into bubbly, slug, slug-annular and annular flows, similarly to conventional-sized tube. The heat transfer was dominated by a nucleate boiling, and an intermittent dryout was observed at the top wall of the tube, while keeping a nucleate boiling state at the bottom wall even in the case of 1.0, 2.0 and 3.0 mm tubes.

Détails

  • Titre original : Heat transfer and flow pattern of boiling flow CO2 in minichannels.
  • Identifiant de la fiche : 2011-0091
  • Langues : Anglais
  • Source : Measures to address climate change. 2010 International Symposium on Next-generation Air Conditioning and Refrigeration Technology: February 17-19, Tokyo, Japan.
  • Date d'édition : 17/02/2010

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