Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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Evaporation Heat Transfer Characteristics of CO2 R-22 and R-134a in a Horizontal Smooth Tube

수평원관 내 CO2 R-22 및 R-134a의 증발열전달 특성에 관한 실험적 연구

  • 윤린 (고려대학교 대학원 기계공학과) ;
  • 황준현 (LG 전자주식회사) ;
  • 최영돈 (고려대학교 기계공학과) ;
  • 김용찬 (고려대학교 기계공학과)
  • Published : 2002.07.01
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Abstract

Evaporation heat transfer coefficients of carbon dioxide($CO_2$), R-22, and R-134a in a horizontal smooth tube were measured and analyzed as a function of heat flux, mass flux, and evaporating temperature. The experiments were carried out by varying heat flux from 10 to 20 $kW/m^2$, mass flux from 170 to 340 $kg/m^2s$, and saturation temperatures of 5 and $10^{\circ}C$. It was found that the heat transfer coefficient of $CO_2$ decreased with a rise of quality due to an earlier liquid-film dryout as compared to R-22 and R-134a. Averaged heat transfer coefficients of $CO_2$ were 22-63% higher than those of R-22 and R-134a at all test conditions. The effects of mass flux and heat flux on averaged heat transfer coefficients were much greater in $CO_2$ than in R-22 and R-134a. When comparing $CO_2$ test results with the correlations in the literature, the existing models yielded large deviations at medium and high qualities. Therefore, a generalized correlation for $CO_2$evaporation heat transfer needs to be developed by including the effects of dryout phenomenon.

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References

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