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Document IIF

Modélisation de l'absorption de vapeur de H2O dans un film tombant de solution aqueuse de Li-Br dans des tubes verticaux en présence d'incondensables.

Modelling of absorption of H2O vapour in falling film of LiBr agueous solution in vertical tubes with presence of non-condensables.

Numéro : pap. n. 220

Auteurs : GARCIA-RIVERA E., CASTRO J., FARNOS J., et al.

Résumé

One of the main reasons of the discrepancies between theoretical predictions made by models of absorbers of H2O-LiBr absorption chillers when they are compared with experimental results under real conditions is the presence of non-condensables gases. These non-condensables gases are inside the shell of the absorption chiller mainly for two reasons: i) air leakages (oxygen-nitrogen); ii) gases produced by corrosion (hydrogen). A mathematical model of falling film absorption of H2O by LiBr aqueous solutions which considers the influence of non-condensable gases has been implemented. The model is semi-empirical, based on Navier Stokes equations together with energy and mass species simplified under the boundary layer hypotheses. Under such conditions, the differential system of equations in partial derivatives, becomes parabolic and could be solved by means of finite difference method in a step by step procedure. Detailed heat and mass transfer balances are applied at the interface to specify the boundary conditions between liquid and gas phases. In order to calculate gradient of air at the interface, the penetration theory is applied in order to avoid a detailed calculation of the gas phase. Numerically the presence of air in the interface results in a pressure drop and consequently in a reduction in heat and mass transfer rates.

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Pages : 8 p.

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Détails

  • Titre original : Modelling of absorption of H2O vapour in falling film of LiBr agueous solution in vertical tubes with presence of non-condensables.
  • Identifiant de la fiche : 30004532
  • Langues : Anglais
  • Source : 10th IIR-Gustav Lorentzen Conference on Natural Working Fluids (GL2012). Proceedings. Delft, The Netherlands, June 25-27, 2012.
  • Date d'édition : 25/06/2012

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