An experimental study on air/water flow behaviours in a 101.6 mm i.d. vertical pipe with a serpentine configuration is presented. The experiments are conducted for superficial gas and liquid velocities ranging from 0.15 to 30 m/s and 0.07 to 1.5 m/s, respectively. The bend effects on the flow behaviours are significantly reduced when the flow reaches an axial distance of 30 pipe diameters or more from the upstream bend. The mean film thickness data from this study has been used to compare with the predicted data using several falling film correlations and theoretical models. It was observed that the large pipe data exhibits different tendencies and this manifests in the difference in slope when the dimensionless film thickness is plotted as a power law function of the liquid film Reynolds number.

Interfacial friction is one of the key variables for predicting annular two-phase flow behaviours in vertical pipes. In order to develop an improved correlation for interfacial friction factor in downward cocurrent annular flow, the pressure gradient, film thickness and film velocity data were generated from experiments carried out on Cranfield University's Serpent Rig, an air/water two-phase vertical flow loop of 101.6 mm internal diameter. The air and water superficial velocity ranges used are 1.42-28.87 and 0.1-1.0 m/s respectively. These correspond to Reynolds number values of 8400-187000 and 11000-113000 respectively. The correlation takes into account the effect of pipe diameter by using the interfacial shear data together with dimensionless liquid film thicknesses related to different pipe sizes ranging from 10 to 101.6 mm, including those from published sources by numerous investigators. It is shown that the predictions of this new correlation outperform those from previously reported studies.Interfacial shear in adiabatic downward gas/liquid co-current annular flow in pipes, Experimental Thermal and Fluid Science, Volume 72, April 2016, Pages 75-87. AbstractInterfacial friction is one of the key variables for predicting annular two-phase flow behaviours in vertical pipes. In order to develop an improved correlation for interfacial friction factor in downward co-current annular flow, the pressure gradient, film thickness and film velocity data were generated from experiments carried out on Cranfield University's Serpent Rig, an air/water twophase vertical flow loop of 101.6 mm internal diameter. The air and water superficial velocity ranges used are 1.42-28.87 and 0.1-1.0 m/s respectively. These correspond to Reynolds number values of 8400-187000 and 11000-113000 respectively. The correlation takes into account the effect of pipe diameter by using the interfacial shear data together with dimensionless liquid film thicknesses related to different pipe sizes ranging from 10 to 101.6 mm, including those from published sources by numerous investigators. It is shown that the predictions of this new correlation outperform those from previously reported studies.

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