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Analyse thermique et chimique du phénomène d'encrassement à l'intérieur de condenseurs pour les applications des tours de refroidissement.

Thermal and chemical analysis of fouling phenomenon in condensers for cooling tower applications.

Numéro : pap. 2198

Auteurs : WU X., CREMASCHI L.

Résumé

Brazed plate heat exchanges (BPHEs) and tube-in-tube heat exchangers (TTHEs) are commonly used in the refrigeration, air conditioning, and food industry as refrigerant-to-water condensers, in which refrigerant rejects heat to water circulating in cooling tower loops. These heat exchangers often suffer from severe fouling issues because as the water in the cooling tower evaporates, the mineral concentration in the remaining water increases. Once the solubility limits are reached, the minerals precipitate and deposit on the heat transfer surfaces: an undesirable yet unavoidable phenomenon. Due to the fouling deposit on the heat transfer surfaces, the thermal resistance between refrigerant and water gradually increases. The fouling resistance depends on several factors such as heat exchanger geometry, heat flux, water quality and water flow rates. The fouling factors penalize the overall effectiveness of the refrigerant condensers and thus must be properly accounted for during the equipment design. Predictions of the fouling allowances during the life service of the condenser characterize the degradation in thermal performance and provide guidelines about the maintenance and service of this type of equipment. In this work, a smooth TTHE was investigated by using a new experimental facility at Oklahoma State University. The aim was to measure the fouling resistance in real time and correlate the data with the water quality and heat flux inside the refrigeration condenser. The fouling resistance in the TTHE was observed to have asymptotic trend and the asymptotic limit was lower than that for BPHEs with soft corrugation angles and higher than that of BHPEs with hard corrugation angles operating at similar conditions. The hydraulic performance was similar as BPHEs with hard corrugation angles. The fouling deposit inside the tube-in-tube heat exchanger was further analyzed by using a CCD camera with a borescope probe and by adopting a chemical digestion process for the fouling particles inside the tubes. Fouling did not deposit uniformly inside the TTHE and it was evident that more fouling was present at the outlet section of the water side. The chemical analysis showed that more than 85% of the fouling material was CaCO3, which was expected from the chemical analysis of the water in critical saturation conditions.

Documents disponibles

Format PDF

Pages : 10 p.

Disponible

  • Prix public

    20 €

  • Prix membre*

    15 €

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

Détails

  • Titre original : Thermal and chemical analysis of fouling phenomenon in condensers for cooling tower applications.
  • Identifiant de la fiche : 30006308
  • Langues : Anglais
  • Source : 2012 Purdue Conferences. 14th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Date d'édition : 16/07/2012

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