Enhanced momentum dissipation in bubble column reactors: design and experimental analysis of swirl flow optimization

This study develops a new momentum-dissipation system for bubble column reactors (BCRs). The operation of BCRs primarily depends on various two-phase flow factors, including geometric configurations (e.g., gas injection), operational conditions (e.g., temperature, pressure, and liquid and gas flow rates), and gas–liquid mass transfer. Among these, the bubble injection geometry plays a particularly important role, influencing parameters such as the gas void fraction and interfacial area. In this study, a bubbly flow rig was built, primarily featuring a bubble-injection mechanism that induces swirl in gas–liquid bubbly flows. Different open-channel configurations were designed to dissipate momentum, which is essential for reducing the liquid’s rotary motion while promoting bubble swirl within the static liquid. This allows for measurement of the liquid-phase velocity field and a qualitative assessment of bubble–liquid slip behavior. PIV technique was applied to single and two-phase systems in a laboratory setting with water and air serving as the working fluids. The experiments assessed the impact of four fins with different geometries, including simple holes and open channels, on velocity vectors across the horizontal plane and, consequently, on liquid momentum. Velocity fields with swirl gas injection were also compared to those without air injection to evaluate the behavior of interacting fluids. Results show that both 90° and 180° open channels produce significantly greater momentum dissipation than the straight and simple hole configurations, with the 90° open channel achieves the highest dissipation overall. Two-plane PIV was used to experimentally map the hydrodynamics of a swirl-injection bubble column reactor equipped with a collar with fins, providing new insight and design guidance for swirl-driven multiphase reactors.