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R-134a : transfert de chaleur lors de la condensation et chute de pression à l'intérieur d'un échangeur de chaleur à plaques brasées

Refrigerant R-134a condensation heat transfer and pressure drop inside a small brazed plate heat exchanger.

Auteurs : LONGO G. A.

Type d'article : Article, Article de la RIF

Résumé

This paper presents the experimental tests on HFC-134a condensation inside a small brazed plate heat exchanger: the effects of refrigerant mass flux, saturation temperature and vapour super-heating are investigated. A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 20 kg/m2.s. For refrigerant mass flux lower than 20 kg/m2.s, the saturated vapour heat transfer coefficients are not dependent on mass flux and are well predicted by the Nusselt analysis for vertical surface. For refrigerant mass flux higher than 20 kg/m2.s, the saturated vapour heat transfer coefficients depend on mass flux and are well predicted by the Akers et al. equation. In the forced convection condensation region, the heat transfer coefficients show a 30% increase for a doubling of the refrigerant mass flux. The condensation heat transfer coefficients of super-heated vapour are 8-10% higher than those of saturated vapour and are well predicted by the Webb model. The heat transfer coefficients show weak sensitivity to saturation temperature. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow and therefore a quadratic dependence on the refrigerant mass flux.

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Pages : 780-789

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Détails

  • Titre original : Refrigerant R-134a condensation heat transfer and pressure drop inside a small brazed plate heat exchanger.
  • Identifiant de la fiche : 2008-1570
  • Langues : Anglais
  • Source : International Journal of Refrigeration - Revue Internationale du Froid - vol. 31 - n. 5
  • Date d'édition : 08/2008

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