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Etude sur les modèles d'écoulement par évaporation et les transferts de chaleur du R22 et du R134a dans des tubes à faible diamètre.

Study on the evaporating flow patterns and heat transfers of R22 and R134a in small diameter tubes.

Auteurs : OH H. K., OH J. T., HONG J. W., et al.

Résumé

Large diameter tubes have been used until comparatively lately. However, small diameter tubes are largely used these days because of their high efficiency in heat transfer and low cost. The study focuses on the experimental research of the flow patterns and heat transfer coefficients during evaporating process of R22 and R134a in small diameter tubes. The evaporating flow patterns of R22 and R134a were observed in pyrex sight glass tubes with ID 2 and 8 mm, respectively, and heat transfer coefficients were measured in smooth horizontal copper tubes with ID 1.77, 3.36 and 5.35 mm. In the flow patterns during evaporating process, the annular flows in ID 2 mm glass tube occurred at a relatively lower mass quality compared to ID 8 mm glass tube. The flow patterns in ID 2 mm glass tube have been fairly discordant with the Mandhane's flow pattern maps. The evaporating heat transfer coefficients in the small diameter tubes were observed to be strongly affected by the size of tube diameters and to differ from those of general predictions in the large diameter tubes. The heat transfer coefficients of ID 1.77 mm copper tube were higher by 20-30% than those of ID 3.36 and ID 5.35 mm copper tube. Also, it was found that it was very difficult to apply well-known previous predictions to small diameter tubes. Based on the data, a new correlation is proposed to predict the evaporating heat transfer coefficients of R22 and R134a in small diameter tubes.

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    20 €

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Détails

  • Titre original : Study on the evaporating flow patterns and heat transfers of R22 and R134a in small diameter tubes.
  • Identifiant de la fiche : 2005-0109
  • Langues : Anglais
  • Source : 21st IIR International Congress of Refrigeration: Serving the Needs of Mankind.
  • Date d'édition : 17/08/2003

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