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Experimental study on critical heat flux characteristics of R134a flow boiling in horizontal helically-coiled tubes.

Author(s) : CHEN C. N., HAN J. T., JEN T. C., et al.

Type of article: Article

Summary

Critical heat flux (CHF) experiments were performed to study the R134a CHF characteristics in horizontal helically-coiled tubes. The stainless steel test sections were heated uniformly, with tube inner diameters of 3.8–11 mm, coil diameters of 135–370 mm, helical pitches of 40–105 mm and heated lengths of 0.85–7.54 m. It was found that the wall temperatures jumped abruptly once the CHF occurred. The CHF values decrease with increasing heated lengths, coil diameters and inner diameters, but the DNB (departure from nucleate boiling) CHF seems independent when length-to-diameter > 200. The coil-to-diameter ratios are more important than length-to-diameter ratios for CHF in helically-coiled tubes, while the helical pitches have little effect on CHF. The CHF value increases greatly with increasing mass flux and decreases smoothly with increasing pressure. It decreases nearly linearly with increasing inlet and critical qualities, but it varies more acutely at xcr < 0.5 than higher critical qualities. New correlations for R134a flow boiling CHF in horizontal helically-coiled tubes were developed for applications. [Reprinted with permission from Elsevier. Copyright, 2010].

Details

  • Original title: Experimental study on critical heat flux characteristics of R134a flow boiling in horizontal helically-coiled tubes.
  • Record ID : 30002646
  • Languages: English
  • Source: International Journal of thermal Sciences - vol. 50 - n. 2
  • Publication date: 2011/02
  • DOI: http://dx.doi.org/10.1016/j.ijthermalsci.2010.10.002

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