Characteristics of slug flow in a narrow rectangular channel under inclined conditions

•Slug flow characteristics in a narrow inclined rectangular duct were investigated.•The velocity of Taylor bubble under inclined conditions was measured.•The Taylor bubble length increases with the inclination angle increasing.•The thickness and velocity of liquid film for inclined cases were measured.•The nose position of Taylor bubble under inclined conditions was measured.

The characteristic parameters of slug flow in a narrow rectangular channel with the cross section of 3.25 mm × 43 mm were measured for various flow rates and channel inclinations. Measurements were carried out by a high speed video camera system and image processing technique. It is found that the Taylor bubble length increases with the gas flow rate and the inclination angle, and decreases with the liquid flow rate. The channel inclinations, the gas and liquid flow rates have significant influences on the thickness and velocity of the liquid film at the bottom of Taylor bubble. The nose position of Taylor bubble is dependent on the two-phase superficial velocity as well as the inclination angle. For the low two-phase superficial velocity, the Taylor bubble velocity and the drift velocity increase with the inclination angle and almost approximate the maximum value for the inclination angle around 30°, while the coefficient C0 decreases with the inclination angle. For the high two-phase superficial velocity, the influence of the inclination angle is insignificant.