Flow pattern and pressure drop of vertical upward gas–liquid flow in sinusoidal wavy channels

Flow patterns and pressure drop of upward liquid single-phase flow and air–water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20 mm, an amplitude of 5.76 mm. Different phase shifts between the side walls of the wavy channel of 0°, 90° and 180° are investigated. The flow phenomena, which are bubbly flow, slug flow, churn flow, and dispersed bubbly flow are observed and recorded by high-speed camera. When the phase shifts are increased, the onset of the transition from the bubbly flow to the churn flow shifts to a higher value of superficial air velocity, and the regions of the slug flow and the churn flow are smaller. In other words, the regions of the bubbly flow and the dispersed bubbly flow are larger as the phase shift increases. The slug flow pattern is only found in the test sections with phase shifts of 0° and 90°. Recirculating gas bubbles are always found in the troughs of the corrugations. The recirculating is higher when the phase shifts are larger. The relationship between the two-phase multipliers calculated from the measured pressure drops, and the Martinelli parameter is compared with the Lockhart–Martinelli correlation. The correlation in the case of turbulent–turbulent condition is shown to fit the data very well for the phase shift of 0° but shows greater deviation when the phase shifts are higher.