Air-Side surface wettability effects on the performance of slit-fin-and-tube heat exchangers operating under wet-surface conditions

Research output: Contribution to journalArticlepeer-review

Abstract

A study of condensate retention and the attendant thermal-hydraulic effect associated with changes in air-side surface wettability is presented for a series of slit-fin-and-tube heat exchangers of identical geometry with controlled wettability covering a wide range of contact angles. An experiment in which the retained mass of air-side condensate was measured under dynamic conditions is described, and the results are analyzed using conventional thermal-hydraulic measurements of j and f. The data demonstrate that for the heat exchangers used in this study, the j factor is not strongly influenced by condensate retention, but the friction factor is significantly reduced for surfaces of increased wettability. Hydrophilic heat exchangers retain much less air-side condensate than do the hydrophobic heat exchangers, and the amount of retention is found to depend on the air-side Reynolds number (Redh) and the rate of latent heat transfer (Ql). Based on an assumption of filmwise condensation, a new model for predicting the mass of retained condensate is described and compared with the steady-sate retention data. The model is successful in predicting retained condensate over a wide range of tested conditions. The potential of this new approach and possible refinements that will add engineering value are discussed.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalJournal of Heat Transfer
Volume131
Issue number5
DOIs
StatePublished - May 1 2009

Keywords

  • Aluminum
  • Condensation
  • Contact angle
  • Fin-and-tube
  • Heat exchangers
  • Retention
  • Wettability

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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