Influence of horizontal return bend on the two-phase flow pattern in a 6.9 mm diameter tube

Ing Youn Chen, Yung Wei Yang, Chi-Chuan Wang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The two-phase flow pattern for air-water mixtures inside a 6.9 mm U-tube is reported to have curvature ratios of 3-7.1. At a lower total mass flux of 50 kg/m2·s and a quality of 0.1, or at a larger curvature ratio of 7.1, no influence on the flow patterns is seen. However, if the curvature ratio is reduced to 3, the flow pattern in the recovery region just after the return bend is temporally turned from stratified flow into annular flow. For a quality larger than 0.4, the annular flow pattern prevails in the entire tube. For G = 400 kg/m2·s and x < 0.01, the size of the plug in the downstream is usually larger than that in the upstream due to the coalesce in the return bend. This coalescence phenomenon continues to further increase the total mass flux at the lower quality region. For a total mass flux above 500 kg/m2·s, the bubbly flow pattern in the upstream region may become intermittent.

Original languageEnglish
Pages (from-to)478-484
Number of pages7
JournalCanadian Journal of Chemical Engineering
Issue number3
StatePublished - 1 Jun 2002


  • Flow pattern
  • Return bend
  • Two-phase flow

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