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Two-phase frictional pressure drop and flow behaviour up- and downstream of a sharp return bend.

Author(s) : DE KERPEL K., DE SCHAMPHELEIRE S., DE KEULENAER T., et al.

Type of article: Article

Summary

In this work, the two-phase flow frictional pressure drop of a refrigerant flow up- and downstream of a sharp return bend is studied. The radius of the return bend is 10.2?mm and the channel inner diameter measures 8?mm. The refrigerant is R134a, the mass flux is varied between 200 and 500?kg/m2?s and the vapour quality x is varied between 0 and 1. The bend orientation is vertical. Upward flow as well as downward flow through the bend is studied. To be able to explain the effect of the return bend on the frictional pressure drop, the two-phase flow behaviour is measured at several locations up- and downstream of the return bend by means of a capacitance sensor. From this capacitance signal, the void fraction and wavelet variance are derived. Close downstream of the return bend the measured pressure gradient is lower than the reference for downward oriented flow. At these locations the void fraction is higher compared to the reference and the wavelet variance is lower compared to the reference measurement, which is consistent with a lower pressure gradient. For upward oriented flow an increase in pressure gradient compared to the reference measurement is observed close downstream of the return bend. At these locations an increase in wavelet variance compared to the reference is observed, which is consistent with the increase in frictional pressure gradient. Upstream the affected length is rather small, less than 10 diameters upstream, downstream the bend effect is more pronounced and present for more than 30 diameters.

Details

  • Original title: Two-phase frictional pressure drop and flow behaviour up- and downstream of a sharp return bend.
  • Record ID : 30017056
  • Languages: English
  • Source: Applied Thermal Engineering - vol. 93
  • Publication date: 2016/01/25
  • DOI: http://dx.doi.org/10.1016/j.applthermaleng.2015.10.064

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