Author(s): Wickenhauser Martin; Minor Hans-Erwin
Linked Author(s):
Keywords: Ir-water two-phase flow; De-aeration pipe; Hydraulics; Slug-flow; Level rise
Abstract: An experimental investigation of vertical de-aeration pipes of pressure tunnels is presented, discussing the maximum average void fraction, the average gas velocity and the translational velocity of elongated air bubbles in air-water two-phase flow in stagnant water. Measurements of the bubble velocity were carried out by using image processing and by correlating the output signals of consecutive conductance probes which detect the air-water boundary. To investigate the effects of air discharge in the pipe, initial pipe water level and pipe diameter on the de-aeration performance, the flow pattern and the water level rise were studied. The pipe diameter has a significant influence on the flow characteristics and the transition boundaries of the different flow types. The maximum average void fraction increases with increasing superficial gas velocity and decreasing pipe diameter. However, the initial water level appears to be insignificant on the maximum average void fraction. The average gas velocity may be predicted well by the correlations developed for small pipe diameters. For larger diameters the drift velocity is significantly higher and increases with increasing diameter of the de-aeration pipe.
Year: 2007