Approach to Two-Phase Flow in Gas Transmission Pipeline Network System

Abstract

Flow of natural gas in a gas pipeline is not entirely single phase flow situation. Even from the well or treatment plant the gas stream might carry along with it appreciable amount of dirts, debris, water or corrosion products from the walls of the pipes, resulting in two or three phase flow situation [1]. Oftentimes the gas might be transported above or below the earth surface or below the sea bed through places of diverse temperature gradients, giving rise to certain undesirable problems. Condensates and hydrates formation are such problems.  The condensates so formed accumulate at low points in the pipes, thereby obstructing flow of gas. Hydrates do form around valves resulting in total blockage or freeze up of the valves. A worst case situation is total obstruction of flow. The end result is increased pressure drop along the pipeline. The approach in the two-phase flow analysis in gas transmission line is to separate the liquid phase from the dry gas phase and develop or deduce the governing expressions for friction factor. The friction factor for two phases so deduced can be injected into any appropriate flow equations to determine the various pressure drop components, overall pressure drop, line throughput or any other flow variables of interest. Two-phase flow analysis approach in this work has enabled the deduction of mathematical models that would be more precise and accurate in predicting flow situations.

Keywords: Mean Flow Velocity; Compressibility Factor; Friction Factor; Liquid Holdup; Gas Holdup; Liquid Velocity Gradient; Gas Velocity Gradient; Liquid and Gas Acceleration Gradient; No Slip; Equivalent length;  Two Phase; Pipeline Efficiency; Equilibrium Constant.