Many efforts have been devoted to investigate air-water two-phase flow pattern in narrow channel during the past decades Wilmarth and Ishii8 measured the air-water flow in narrow vertical and horizont

Overall, these studies have contributed to a better understanding of air-water two-phase flow pattern in narrow channels, and have provided useful data and criteria for design and optimization of various industrial applications, such as heat exchangers, microreactors, and fuel cells. However, there are still challenges and uncertainties in predicting and controlling the flow pattern in narrow channels, especially when dealing with complex geometries, high pressures, and variable properties of the fluids. Further research is needed to develop more accurate and robust models and experimental techniques, and to explore the effects of various factors on the flow pattern, such as surface tension, gravity, turbulence, and wall roughness