Excessive liquid carryover in T-junction due to splitting nature of two-phase flow causes serious issues in piping system. A three-dimensional numerical model is employed to investigate two-phase flow split behavior of slug flow in a circular-section regular T-junction with 0.0752 m diameter. The Volume of Fraction method combined with k-ε turbulence model and initial sinusoidal perturbation in ANSYS FLUENT is adopted to characterize the effect of slug flow behavior on the phase separation efficiency. The preliminary result reveals that the simulation work can study slug flow split in great detail and the slug characteristic plays an important role in understanding split behavior.

Liquid carryover in T-junction due to splitting nature of two-phase flow causes serious issues for downstream equipment which is not designed to handle excessive liquid. In this paper, the phenomena of liquid carryover in T-junctions were analyzed using the Volume of Fraction (VOF) together with the k-ε turbulence model. T-junction separation efficiency was measured through mass flow rate fraction of air and water between the branch and main arm over a range of diameter ratios 0.6 to 1.0, water superficial velocity 0.186 to 0.558 m/s and air superficial velocity 4 to 8 m/s. The results showed simulation model was successfully validated with average deviation of less than 5% and can be used to predict phase split of slug flow in T-junction. The numerical model confirmed the significant influence of diameter ratio and superficial velocities of air and water on phase split. Reduced T-junction delivers better separation performance compared to regular T-junction. In slug flow regime, T-junction’s performance can be improved by either decreasing air velocity or increasing water velocity. A new dimensionless parameter, namely the area under the curve of separation efficiency (S), was proposed and proved as a qualified judging criteria for evaluating phase separation efficiency of T-junctions.

This article presents a design and commissioning of a multiphase flow loop, which was developed for scrutinizing the partial phase separation characteristics of pipe Tees. Its length is 9m and its primary diameter is 0.078m (3 inches). For the ease of modification, its design was kept modular, so that it could be used for testing various other pipe profiles. To validate this flow loop, the separation of a stratified-wavy flow was tested in a regular diameter ratio pipe Tee, and the gathered results were compared with previously published data. A good agreement was observed between the two data sources, which suggests that this flow loop is suitable for a further experimentation.

In the offshore platform, T-junction has been extensively used as preliminary gas-liquid separator due to its compact design. Frequently, a sudden slug generation causes liquid carryover issues leading to excessive liquid in the gas feed for downstream equipment. Geometry features of T-junction and slug flow are believed to be the root cause of this problem. Based on the literature review, previous works mostly focused on improving two-phase separation in the standard T-junctions without taking into account the impact of inlet flow regime. Moreover, there is no published research on the separation performance of converging T-junction, which is a promising design. The objective of this research is to numerically evaluate the hypothesis that converging T-junction yields better phase separation under slug flow compared with regular and reduced T-junctions. Three-dimensional Computational Fluid Dynamics (CFD) software FLUENT 17.2 and specialized User Defined Functions was utilized to study the evolutionary process of air-water slug flow and its phase separation behavior in converging T-junctions over eight different geometry designs. The incompressible Volume of Fluid (VOF) method was used to capture the transient distribution of segregated gas-liquid interface. The validity of the present model was compared with the experimental data taken from the air-water two-phase flow in 3-inch diameter main pipe of T-junction. The validated model gave a strong foundation to proceed with converging T-junction simulation. The research found that the converging T-junction can increase by upto 20% of separation efficiency compared with regular and reduced T-junction at the same operating conditions. Moreover, the converging T-junction with the main and converging diameter ratio of 0.67 and 0.4, respectively, to be optimal in improving the phase separation over a wide spectrum of air and water superficial velocities.

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