Abstract
The air-water two-phase flow plays an important role in many applications of industry fields. Usually, a 90-degree bend is used to connect pipes for changing the direction of flow which influences the two-phase flow pattern. In this paper, the effect of 90-degree bend under different ranges of gas and liquid superficial velocities on the two-phase flow patterns in the horizontal pipe located after the bend was experimentally investigated, and then results were presented and compared in a two-phase flow pattern map. Also, tomographic images and probability density functions were used to capture the cross-section void fraction and its distribution for the two-phase flow patterns. The results revealed that at low liquid and gas flow rates, a stratified-wavy flow pattern was observed as a dominant flow pattern. While the wavy-annular and semiannular flow patterns were observed at a high range of gas flow rates in the horizontal pipe. The results also showed that at the high range of liquid flow rate, bubbly, plug, slug, stratified-wavy, and wavy-annular flow patterns were observed in the horizontal pipe when the gas flow increased. The tomographic images and probability density functions gave good agreement with the experimental observations and results.
Highlights
The air-water two-phase flow exists in many mechanical and chemical applications such as that in transportation pipelines and power generation stations, it plays an important role in other scientific fields, such as physics, biology, and meteorology [1]
The results reported three configurations of the flow: homogeneous flow when the Froude number (Fr) is equal to one, the gas phase moves to the external axial side of the curve and the liquid phase tends to flow in the internal axial side when the Fr is less than one, the gas tends to move to the internal axial side of the bend when the Fr is greater than one
The increased value of the superficial velocity of water (Usl) from 0.157 to 0.314 m/s has no significant effect on the flow patterns of the vertical flow lines, where the flow patterns have been observed in the vertical section as a bubbly flow when the Usg value was 0.064 m/s, slug flow when the Usg value was in the range from 0.299 to 0.991 m/s and churn flow when the Usg value was in the range from 1.496 to 5.26 m/s
Summary
The air-water two-phase flow exists in many mechanical and chemical applications such as that in transportation pipelines and power generation stations, it plays an important role in other scientific fields, such as physics, biology, and meteorology [1]. Much attention has been given by previous studies to investigate the two-phase flow behavior and its pattern in elbows and bents pipes. Gardner and Neller [4] studied the air-water two-phase flow behavior in a 90-degree bend with an internal diameter of 76 mm. The study investigated the impact of bend angular (φ) and the influence of increasing the superficial velocities on the two-phase flow behavior. The results presented a correlation for dimensionless parameters between the centrifugal and gravitational forces to represent the Froude number for different two-phase flow patterns. Kim et al [7] presented an experimental study to investigate the two-phase flow patterns for the airwater flow in a 90-degree elbow of an internal diameter of 50.3 mm. The bubbly flow regime in a developed region in a horizontal pipe after the elbow was observed in the experiments
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