Gas-liquid flow through horizontal periodic open cellular structures

Structured catalysts like periodic open cellular structures and catalytic static mixers are gaining attention for their ability to enhance heat and mass transfer in continuous flow reactors. However, pressure drop and hydrodynamic behaviour under two-phase flow remain poorly understood, particularly in horizontally oriented flow reactors operating at low superficial velocities relevant to gas-liquid reactions. These configurations are increasingly important in modular and multi-pass reactor systems, where vertical operation may be impractical. In this study, we conducted single phase pressure drop measurements through POCS and packed beds and compared them with established literature models. We then performed two-phase gas-liquid pressure drop experiments and developed a Lockhart-Martinelli type correlation through a combination of semi-empirical analysis and intuitive reasoning. The proposed model predicts two-phase pressure drop with an accuracy within ±20 %. Notably, we observed flow regime transitions from stratified to slug flow, occurring at much lower velocities than those reported for empty tubes or packed beds. These findings provide a practical framework for the design of low flow-resistance, horizontally operated reactors with structured catalysts, enabling better control in multiphase systems such as hydrogenation and dehydrogenation processes. • Low superficial velocities investigation of single- and two-phase pressure drop-in horizontally oriented diamond lattice periodic open cellular structures (POCS). • Characterization of flow regime transitions between stratified and slug flow at superficial low gas and liquid velocities. • Development of a Lockhart-Martinelli type correlation capable of predicting two phase pressure drop within 20% accuracy. • Identification of dynamic pressure fluctuation patterns, including frequency and duty cycle, at low superficial gas velocities.