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Evaluation des propriétés optimales des coulis de glace grâce à des équations simples et aux propriétés de la solution aqueuse.

Estimating optimal ice slurry properties using simple equations and properties of the aqueous solution.

Numéro : pap. ID: 283

Auteurs : MELINDER Å.

Résumé

Aqueous solutions used as single-phase secondary fluids can also be used below the freezing point as ice slurry, a fluid consisting of liquid and ice. It is not as easy to determine thermophysical properties when aqueous solutions are used as two-phase ice slurry as when used for single-phase liquids. One main reason is that ice particles in a system change form and size with time. Values obtained from measurements in lab rigs are strictly valid only for the batch in case and at that specific time. Results from experiments done over the years in various lab rigs in research centres have often been compared to what equations for liquids with solid particles give although the values at times differ much. Such equations may be used to compare ice slurry properties for different fluid types and to find optimal conditions in a particular application. This paper presents ice fraction, density, enthalpy, viscosity and thermal conductivity for aqueous solutions of ethylene glycol and potassium formate based on fluid properties and mentioned equations. Diagrams help us compare the fluids for certain operational temperatures and initial freezing point temperatures or additive fractions. The relative differences between fluids and operational conditions will likely be similar to what ice slurry in a real plant gives, providing valuable clues for choice of fluid and suitable operational conditions. A conclusion from examples given is that the best performance is obtained with an initial freezing point equal to the operation temperature at the end of the user unit, giving maximal change in ice fraction and enthalpy. The dynamic viscosity does not differ very much from the viscosity of single-phase while the thermal conductivity is higher. The high density of potassium formate may give less even distribution of ice in pipes.

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Pages : 8 p.

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Détails

  • Titre original : Estimating optimal ice slurry properties using simple equations and properties of the aqueous solution.
  • Identifiant de la fiche : 30002398
  • Langues : Anglais
  • Source : Proceedings of the 23rd IIR International Congress of Refrigeration: Prague, Czech Republic, August 21-26, 2011. Overarching theme: Refrigeration for Sustainable Development.
  • Date d'édition : 21/08/2011

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