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R404A condensing under forced flow conditions inside smooth, microfin and cross-hatched horizontal tubes.

Author(s) : INFANTE FERREIRA C. A., NEWELL T. A., CHATO J. C., et al.

Type of article: Article, IJR article

Summary

Two-phase heat transfer coefficient characteristics of R404A condensing under forced flow conditions inside smooth, microfin and cross-hatched horizontal tubes are experimentally investigated. Experimental parameters include a lubricating polyol ester oil concentration varied from 0 to 4%. The test runs were done at average inlet saturated condensing temperatures of 40 °C. The inlet vapor was kept at saturation (quality=1.0). The mass fluxes were between 200 and 600 kg/m² s, and the heat fluxes were selected to obtain a quality of 0.0 at the outlet of the test section, varying from 5 to 45 kW/m². The heat transfer enhancement factor varied between 1.8 and 2.4 for both microfin and cross-hatched tubes. The larger values applied for larger mass fluxes for the cross-hatched tube and smaller mass fluxes for the microfin tube. Enhancement factors increased as oil concentration increased up to oil concentrations of 2%. For higher oil concentrations the enhancement decreased especially at high mass fluxes, the cross-hatched tube being less sensitive to oil contamination. Pressure drop in the test section increased by approximately 25% as the oil concentration increased from 0 to 4%. The results from the experiments are compared with those calculated from correlations reported in the literature. Moreover, modified correlations for the condensation heat transfer coefficient are proposed for practical applications.

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Pages: 433-441

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Details

  • Original title: R404A condensing under forced flow conditions inside smooth, microfin and cross-hatched horizontal tubes.
  • Record ID : 2003-1688
  • Languages: English
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 26 - n. 4
  • Publication date: 2003/06

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