Effect of riser base and flowline gas injection on the characteristics ofgas-liquid two-phase flow in a vertical riser system

Pressure gradient (PG) is vital in the design/operation of process equipment e.g. in determining pumpingrequirements and has direct effect on capital and running costs. Here, we report a gas-liquid experimentalstudy using a large diameter pipeline system. Pressure was measured at two locations of each sectionof the upward and downward flowing sections. PG was then determined for a wide range of superficialvelocities: Usg = 0-30 m/s and usl = 0.07-1.5 m/s. We found varying trends in pressure gradient behaviourbetween upward and downward flow under similar conditions: From bubbly to annular flow. We give atheoretical account due to the different physical mechanisms. PG values based on prevailing conditionsand flow direction were compared. We show that the satisfactory prediction of PG is highly dependent onflow direction and limits of experimental conditions. These factors can have important implications for thedesign and operation of fluid pipelines in the process, nuclear and oil and gas industries.