(591h) The Effect of Surfactant Additives on the Onset of Flooding in Gas-Liquid Annular Flows

The Effect of Surfactant Additives on the Onset of Flooding in Gas-Liquid Annular Flows

Zadrazil I., Markides C.N. and Matar, O.K.

Flooding in counter-current gas-liquid systems is characterised by an onset of flow reversal of at least a part of the liquid phase from a counter-current to a co-current state adverse to gravity. These complicated non-linear effects appear typically when the gas phase is turbulent. Although flooding has been investigated extensively both phenomenologically and experimentally, the criteria for the onset of flooding and related interfacial instabilities remain unclear. This phenomenon is of high industrial importance; it can be found in the oil-and-gas industry (e.g. raisers in gas-liquid oil wells) or during emergency events in nuclear reactor core.

Flooding has been investigated previously in various geometries: cylindrical tubes, trickle beds and commercial random and structured packings. In this work, we focused on flooding in tubes with an emphasis on the dynamics of gas-liquid flows and on the effect of surfactant additives on flow regime transitions using high-speed shadowgraphy based imaging and differential pressure drop measurements. The measurements were performed using a facility consisting of 4 m long, 32.4 mm nominal bore poly(methyl methacrylate) (PMMA) pipe, where the annular flow was introduced at the top of the pipe using a specially designed porous injector, which forms circumferentially uniform liquid films. The investigated liquid and gas Reynolds numbers were in the range of Re_L = 200 – 6,000 and Re_G = 0 – 100,000, respectively. The visualisation section was enclosed in an optical correction box in order to minimize any distortions that would arise from the round PMMA test section.

In this paper results will be presented from an extensive effort to characterize the influence of surfactant additives, their bulk concentration and the liquid and gas Reynolds numbers on the flow regime characteristics in counter-current gas-liquid flows. The results will include qualitative axial and radial high-speed recordings as well as quantitative measurements of differential pressure drop, and statistics of droplet and bubble size, droplet velocity, and frequency of large waves.