Horizontal-Tube Falling-Film evaporation with structured surfaces

M. C. Chyu, A. E. Bergles

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

Extensive experimental tests for tubes with commercial structured surfaces in a horizontal single-tube falling-film evaporator were conducted. The test sections were hollow copper cylinders with GEWA-T, Thermoexcel-E, or High Flux surfaces electrically heated by inserted cartridge heaters. A smooth surface cylinder was also tested for reference. All tubes were tested in both pool boiling and falling-film evaporation with water. The results reveal that falling-film evaporation provides much higher heat transfer coefficients than pool boiling in the low heat flux, convective region. The GEWA-T surface enhances heat transfer through its increased and accessible area, while Thermoexcel-E and High Flux demonstrate high heat transfer performances because of enhanced nucleate boiling. The falling-film evaporation data for the structured surfaces either merge or show a tendency to merge with the respective pool boiling curves at high heat fluxes. Unusual incipient boiling behavior of Thermoexcel-E and the effects of factors such as surface aging, surface subcooling, film flow rate, liquid feed height, and rate of heat flux change, are described.

Original languageEnglish
Pages (from-to)518-524
Number of pages7
JournalJournal of Heat Transfer
Volume111
Issue number2
DOIs
StatePublished - May 1989

Keywords

  • Augmentation and Enhancement
  • Evaporation
  • Natural Convection

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