Partager

Document IIF

Rendement global des ailettes de surface et angle sec pour les évaporateurs d'ammoniac à tubes ailetés.

Overall surface fin efficiency and dry angle for ammonia finned tube evaporators.

Numéro : 0164

Auteurs : KÆRN M. R., JENSEN J. K., MARKUSSEN W. B., KRISTOFERSSON J.

Résumé

The use of the overall surface efficiency for modelling finned-tube surfaces is frequently encountered in the scientific literature. The method relies on the assumption of a constant temperature along the external surface of the tube. The appropriateness of this assumption depends on the tube material, wall thickness and the fin spacing. Typically, ammonia finned-tube evaporators employ thin walled stainless steel tubes with large fin spacing for the accommodation of frost during long frosting periods. The tubes have a thermal conductivity about 25 times lower than that of copper and 15 times lower than that of aluminium. The low thermal conductivity leads to temperature changes along the external tube surface in the axial direction and the assumption of the overall surface efficiency loses its validity. The current paper investigates the applicability of the overall surface efficiency both analytically and numerically. The objective was to derive and verify a simple expression for the tube efficiency, similar to the fin efficiency, which takes into account internal as well as external dissimilar convection coefficients. Furthermore, the effect of two-phase stratification and variations in dry angle were investigated numerically.

Documents disponibles

Format PDF

Pages : 9 p.

Disponible

  • Prix public

    20 €

  • Prix membre*

    Gratuit

* meilleur tarif applicable selon le type d'adhésion (voir le détail des avantages des adhésions individuelles et collectives)

Détails

  • Titre original : Overall surface fin efficiency and dry angle for ammonia finned tube evaporators.
  • Identifiant de la fiche : 30029756
  • Langues : Anglais
  • Sujet : Technologie
  • Source : 15th IIR-Gustav Lorentzen Conference on Natural Refrigerants (GL2022). Proceedings. Trondheim, Norway, June 13-15th 2022.
  • Date d'édition : 13/06/2022
  • DOI : http://dx.doi.org/10.18462/iir.gl2022.0164
  • Document disponible en consultation à la bibliothèque du siège de l'IIF uniquement.

Liens


Voir d'autres communications du même compte rendu (169)
Voir le compte rendu de la conférence

Indexation