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Experimental study of evaporation heat transfer characteristics of refrigerants R134a and R407C in horizontal small tubes.

Author(s) : LIE Y. M., SU F. Q., LAI R. L., et al.

Type of article: Article

Summary

An experiment is carried out in the article to investigate the characteristics of the evaporation heat transfer for R134a and R407C flowing in horizontal small tubes having the same inside diameter of 0.83 or 2.0 mm. In the experiment for the 2.0-mm tubes, the refrigerant mass flux is varied from 200 to 400 kg/m2.s, imposed heat flux from 5 to 15 kW/m2, inlet vapour quality from 0.2 to 0.8 and refrigerant saturation temperature from 5 to 15°C. In the study, the effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured evaporation heat transfer coefficient are examined in detail. The experimental data clearly show that both the R134a and R407C evaporation heat transfer coefficients increase almost linearly and significantly with the vapour quality of the refrigerant, except at low mass flux and high heat flux. Besides, the evaporation heat transfer coefficients also increase substantially with the rises in the imposed heat flux, refrigerant mass flux and saturation temperature. At low R134a mass flux and high imposed heat flux, the evaporation heat transfer coefficient in the smaller tubes may decline at increasing vapour quality when the quality is high, due to the partial dryout of the refrigerant flow in the smaller tubes at these conditions. Finally, an empirical correlation for the R134a and R407C evaporation heat transfer coefficients in the small tubes is proposed. [Reprinted with permission from Elsevier. Copyright, 2005].

Details

  • Original title: Experimental study of evaporation heat transfer characteristics of refrigerants R134a and R407C in horizontal small tubes.
  • Record ID : 2006-2272
  • Languages: English
  • Source: International Journal of Heat and Mass Transfer - vol. 49 - n. 1-2
  • Publication date: 2006/01

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