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A study of falling film evaporation on finned tubes.

Number: pap. A4-130

Author(s) : CHIEN L. H., CHEN R. H.

Summary

This study investigates the evaporation heat transfer performance of R134a falling film on three horizontal tubes in a vertical column. This study tested three kinds of tubes, a smooth tube, and a fin tube of 0.4 mm fin height, 60 FPI (fins per inch). Experiments were performed at saturation temperatures of 10, 20 and 26.7?. The liquid flows through a liquid feeder with a row of circular holes at a rate of 0.0075~0.0363 kg/ms, and heat fluxes varied from 4.5 to 48.5 kW/m2. The test results show that the heat transfer coefficient of the smooth tube increases with increasing heat flux, fluid temperature, and it increases slightly with increasing flow rate before dry-out occurs. At low flow rates (less than 0.015 kg/ms) or Ref (= 255), the fin tube is in thin film evaporation mode, which is revealed by its high heat transfer coefficient, and at high flow rates (0.0225, 0.03, and 0.0375 kg/ms) the falling film evaporation curves are similar to those in pool boiling. The fluid temperature and the flow rate have only minor influence on heat transfer coefficient before dry-out occurs. The fin tube enhances the heat transfer coefficient by 6.3~8.29 fold.

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Pages: 8 p.

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Details

  • Original title: A study of falling film evaporation on finned tubes.
  • Record ID : 30004702
  • Languages: English
  • Source: ACRA2010. Asian conference on refrigeration and air conditioning: Tokyo, Japan, June 7-9, 2010.
  • Publication date: 2010/06/07

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