Effect of upstream conditions on the two phase flow in the large diameter vertical pipe

Two phase flow in large diameter vertical pipes is of considerable importance to various fields of multiphase flows. Recently, due to increase in demand in various energy sectors considerable attention has been paid in understanding the flow behavior in large diameter vertical pipes. This paper reports the experimental results of flow pattern identification in relatively large diameter (254mm) vertical pipe. The present work also investigates the effect of upstream conditions on the flow patterns occurring in the vertical test section. The observed flow patterns are classified as bubbly, agitated bubbly, unstable slug and churn/froth flow. Absence of hydrodynamic slugging i.e. non occurrence of Taylor bubble in the riser is also reported. It is found that agitated bubbly and churn/froth type of flows dominates in the vertical large diameter pipe under the condition where conventional small diameter pipe indicates slug flow. Experimental results demonstrate the sensitivity of the flow patterns occurring in the vertical section with the upstream conditions in the flowline. The statistical analysis performed on the data along with visual observations, suggests that liquid slugs formed in flowline dissipate as they travelled up the riser, due to the high velocity distorted bubble clusters