Experimental investigations on air-water two-phase flow through a minichannel U-bend

Experimental investigations are reported for air-water two-phase flow through a 2.25 mm circular minichannel U-bend. Influence of radius of curvature is established by developing two minichannel U-bends with radius of curvature as 6 mm and 12 mm. T-junction is used as a mixing geometry for air and water. The superficial gas and liquid velocities are set in the range of 0.0419-0.4192 m/s. Total five different flow patterns such as plug, slug, bubbly, bubbly-plug and deformed plug are observed. Flow pattern transition maps are developed as a function of radius of curvature. The positional shift of gas bubbles within the curved portion of minichannel U-bend minichannel for bubbly, plug and deformed plug flow is identified. The influence of radius of curvature on hydrodynamics of Taylor bubble flow such as void fraction, liquid holdup, Taylor bubble velocity, Taylor bubble and liquid slug length is investigated. The radius of curvature with other flow parameters is found to have significant effect on two-phase flow patterns, its transition boundaries and hydrodynamics of Taylor bubble flow.