This study examines the two-phase flow pattern change and frictional pressure loss pertaining to the sudden flow area expansion from a small diameter tube into small rectangular channels. It is found that a unique flow pattern "liquid jet-like flow pattern" occurs at a very low quality region of G = 100 kg / m2 s in a test section of 3 mm × 9 mm. This flow pattern is almost inconceivable for the 3 mm × 6 mm test section. The pressure difference usually increases with vapor quality but a setback is encountered provided that the liquid jet flow pattern prevails. A phenomenal observation suggests that a conceivable reduction of the pressure difference is related to the liquid jet-like flow pattern, yet a flat or level-off of the pressure difference is seen when the liquid jet-like flow is less pronounced. By contrast, an appreciable increase of pressure difference is seen when the liquid jet-like flow pattern is completely gone. The measured pressure differences are compared with existing correlations/models, whereas none of them gives satisfactory predictions against the present data. It is found that a slight modification to the empirical constant K of Wadle's correlation may give rise to a fair improvement of the predictive ability.
|Number of pages||11|
|Journal||Experimental Thermal and Fluid Science|
|State||Published - 1 Nov 2007|
- Flow pattern
- Sudden expansion
- Two-phase flow