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Saturated flow boiling heat transfer of R407C and associated bubble characteristics in a narrow annular duct.

Author(s) : HSIEH F. C., LI K. W., LIE Y. M., et al.

Type of article: Article

Summary

Experiments are conducted here to investigate how the channel size affects the R407C saturated flow boiling heat transfer and associated bubble characteristics in a horizontal narrow annular duct. The gap of the duct is fixed at 1.0 and 2.0 mm in this study. The measured data indicate that the saturated flow boiling heat transfer coefficient increases with a decrease in the duct gap. Besides, raising the imposed heat flux can cause a significant increase in the boiling heat transfer coefficients. However, the effects of the refrigerant mass flux and saturated temperature on the boiling heat transfer coefficient are milder. The results from the flow visualization show that the mean diameter of the bubbles departing from the heating surface decreases noticeably at increasing R407C mass flux. Moreover, the bubble departure frequency increases at reducing duct size and at a high imposed heat flux many bubbles generated from the cavities in the heating surface tend to merge together to form big bubbles. Meanwhile comparison of the present heat transfer data for R407C with R134a in the same duct and with some existing correlations is conducted. Furthermore, correlation for the present R407C saturated flow boiling heat transfer data is proposed. Additionally, the present data for some quantitative bubble characteristics such as the mean bubble departure diameter and frequency and the active nucleation site density are also correlated. [Reprinted with permission from Elsevier. Copyright, 2008].

Details

  • Original title: Saturated flow boiling heat transfer of R407C and associated bubble characteristics in a narrow annular duct.
  • Record ID : 2009-1030
  • Languages: English
  • Source: International Journal of Heat and Mass Transfer - vol. 51 - n. 15-16
  • Publication date: 2008/07

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