An experimental investigation was conducted on the vertically upward flow of air-water two-phase in a channel with a square cross-section. The hydraulic diameter of the channel was 10mm; the superficial air velocity was 0.04-100m/s; the superficial water velocity was 0.001- 6 m/s. The typical flow patterns
creep flow and rivulet flow
were observed by flow visualization with a DV camera and an endoscope
and the flow pattern map and flow pattern transition boundaries were obtained. The thickness of liquid film of the creep flow and the annular flow in the square channel was measured by a γ-ray instrument. The results show that the mechanism to form the creep flow in the square channel is different from that to form the rivulet flow in a circular tube and a secondary flow exits in the square channel. The phase distribution on the inner wall of the noncircular channel indicates that the influence of the channel geometry results in the steeper radial distribution of the phases and velocities
and eventually turbulent secondary flow. With the increase in the gas velocity
the film thickness at center of the wall is greater than that at corner
indicating the significant effect of the secondary flow on the phase distribution in the noncircular channel.
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references
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