Heat transfer enhancement by Marangoni convection in the NH3-H2O absorption process

Yong Tae Kang, Takao Kashiwagi

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The objectives of this paper are to quantify the effect of Marangini convection on the absorption performance for the ammonia-water absorption process, and to visualize Marangoni convection that is induced by adding a heat transfer additive, n-octanol. A real-time single-wavelength holographic interferometer is used for the visualization using a He-Ne gas laser. The interface temperature is always the highest due to the absorption heat release near the interface. It was found that the thermal boundary layer (TBL) increased faster than the diffusion boundary layer (DBL), and the DBL thickness increased by adding the heat transfer additive. At 5 s after absorption started, the DBL thickness for 5 mass% NH3 without and with the heat transfer additive was 3.0 and 4.5 mm, respectively. Marangoni convection was observed near the interface only in the cases with heat transfer additive. The Marangoni convection was very strong just after the absorption started and it weakened as time elapsed. It was concluded that the absorption performance could be improved by increasing the absorption driving potential (xvb - xvi) and by increasing the heat transfer additive concentration. The absorption heat transfer was enhanced as high as 3.0-4.6 times by adding the heat transfer additive that generated Marangoni convection.

Original languageEnglish
Pages (from-to)780-788
Number of pages9
JournalInternational Journal of Refrigeration
Volume25
Issue number6
DOIs
Publication statusPublished - 2002 Sep

Keywords

  • Absorption system
  • Ammonia/water
  • Enhancement
  • Heat transfer
  • Marangoni convection

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering

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