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Transfert de chaleur avec congélation dans un échangeur de chaleur à surface raclée.

Heat transfer with freezing in a scraped surface heat exchanger.

Auteurs : BEN LAKHDAR M., CERECERO R., ALVAREZ G., et al.

Type d'article : Article

Résumé

An experimental study was carried out on a scraped surface heat exchanger used for freezing of water-ethanol mixture and aqueous sucrose solution. The influence of various parameters on heat transfer intensity was established: product type and composition, flow rate, blade rotation speed, distance between blades and wall. During starting (transient period) the solution is first supercooled, then ice crystals appear on the scraped surface (heterogeneous nucleation) and no more supercooling is observed. It seems that, when blades are 3 mm far from the surface, a constant ice layer is formed having this thickness and acting as a thermal resistance. But when the blades rotate at 1 mm from the surface, periodically all the ice layer is removed despite the fact that the surface is not really scraped. This could simplify ice generator technology. An internal heat transfer coefficient was defined; it depends mainly on rotation speed. Correlations were proposed for its prediction, which could be applied, at least as a first approach, for the most common freezing applications of scraped surface heat exchanger i.e. ice creams (which are derived from sucrose solutions) and two-phase secondary refrigerants (which are principally ethanol solutions).

Détails

  • Titre original : Heat transfer with freezing in a scraped surface heat exchanger.
  • Identifiant de la fiche : 2005-1737
  • Langues : Anglais
  • Source : Applied Thermal Engineering - vol. 25 - n. 1
  • Date d'édition : 01/2005

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