Influence of Direct and Co-Flow Pre-Injection of a Gas Phase on Gas–Liquid Two-Phase Flow through a Vertical Minichannel

Abstract

The influence of pre-injection of a gas phase on gas–liquid two-phase flow through a vertical minichannel is experimentally investigated. Circular minichannel of 2 mm inner diameter is considered for the investigations. Air is used as a gas phase and water is used as a liquid phase. The superficial gas and liquid velocities are kept as 0.0531–0.2653 and 0.1062–0.2653 m/s, respectively. Inlet premixing of gas–liquid two-phase flow is achieved with an injector equipped with a nozzle to inject a gas phase. Three nozzles are developed with inner diameters of 0.7, 2, 2.5 mm. Direct injection and co-flow pre-injections of gas phase are obtained with various positions of a nozzle (0, 25 and 50 mm) in an injector. Flow patterns such as bubbly flow, Taylor bubble flow and slug-annular flow are observed and captured using an EXILIM high-speed camera. The influence of nozzle size and its positions in an injector on the hydrodynamics of Taylor bubble flow as well as two-phase pressure drop are analysed in detail. Inlet premixing and two-phase flow hydrodynamics have significant influence of gas-phase pre-injection in a vertical minichannel.