Numerical evaluation of separation efficiency in converging T-junction with slug flow

Abstract

Purpose

Excessive liquid carryover in T-junction presents a serious operational issue in offshore production platform. Slug flow and diameter ratio of T-junction are considered as two major factors causing liquid carryover. Regular and reduced T-junction are being used as partial phase separator but their efficiency is low. Converging T-junction with two distinct diameters (primary and secondary) in branch arm is used to improve the phase separation efficiency. The motivation is to combine specific feature of regular and reduced T-junction to increase separation efficiency of existing T-junction without involving too much operational workover. The purpose of this paper is to numerically evaluate the separation efficiency of a converging T-junction design. The present model and its methodology was validated with in-house experimental data for 3 inches diameter flow loop.

Design/methodology/approach

The slug flow regime was simulated using incompressible Eulerian mixture model coupled with volume of fluid method to capture the dynamic gas-liquid interface.

Findings

The analyses concluded that T-junction with primary-secondary branch arm diameters combination of 1.0-0.5 and 0.67-0.40 managed to achieve 95 per cent separation efficiency. The research also confirmed that over reduction of T-junction secondary diameter ratio below 0.2 will lead to decrease in separation efficiency.

Research limitations/implications

The present research is limit to air/water two-phase flow but the general results should be applicable for wider application.

Practical implications

The proposed design limited excessive workover and installation for current and existing T-junction. Hence, cutting down installation cost while improving the separation efficiency.

Social implications

The present research resulted in higher separation efficiency, cutting down production down time and lead to operational cost saving.

Originality/value

The present research proposes an original and new T-junction design that can increase phase separation efficiency to over 90 per cent. The finding also confirmed that there is a limitation whereby smaller diameter ratio T-junction does not always resulted in better separation.

Citation

Pao, W. and Memon, Z.Q. (2020), "Numerical evaluation of separation efficiency in converging T-junction with slug flow", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 30 No. 7, pp. 3515-3534. https://doi.org/10.1108/HFF-07-2019-0524