Study on the gas-liquid two-phase flow patterns for hydrogen production from electrolytic water.

Hydrogen production from electrolytic water is one of the most crucial techniques for generating green hydrogen. If the flow of hydrogen gas and alkali water in the transportation pipe exhibits slug flow, vibrations may occur, leading to potential accidents. The study of preventing slug flow is significant for pipe design. However, currently, there is no available research on the gas-liquid two-phase flow patterns of hydrogen gas and alkali water. Therefore, this study investigates the gas-liquid two-phase flow patterns in the pipe transporting hydrogen gas and alkali water and provides recommendations to prevent slug flow. Firstly, a numerical model based on the Volume of Fluid (VOF) method is established to simulate the two-phase flow of hydrogen gas and alkali water. Then, the effects of hydrogen gas and alkali water flow rates, pipe orientation, pipe diameter, and pipe length on the gas-liquid two-phase flow patterns are studied. Subsequently, the two-phase flow patterns are analyzed under different pipe layouts, including horizontal-vertical pipes, horizontal-horizontal pipes, horizontal-vertical-horizontal pipes, etc. The research reveals that increasing the pipe diameter, reducing the pipe length and increasing the hydrogen gas flow rate can effectively prevent slug flow in vertical pipes. Additionally, horizontal pipes and horizontal-horizontal pipes are less likely to experience slug flow. Furthermore, the consecutive appearance of two elbows induces slug flow even at higher hydrogen apparent velocities. Extending the length of the pipe between two consecutive elbows can effectively suppress the occurrence of slug flow. The present work can provide an important reference for the design of pipes used in hydrogen production from electrolytic water. [Display omitted] • The flow pattern of hydrogen-alkali water two-phase flow is studied. • Six different structures of pipes are studied, especially those containing elbows. • Two consecutive elbows with short distances can easily induce a slug flow. • Altering flow rates and pipe structural parameters can suppress slug flow. [ABSTRACT FROM AUTHOR]