In this paper, the characteristics of stratified-annular flows such as flow patterns, phase distributions, liquid height, and pressure gradient were studied using a traversing two-energy gamma densitometer, high-speed video recordings and pressure transducers.
The experiments were carried out in a 0.069m diameter and 50 m long horizontal pipe. The fluid system consist of high density gas, SF6, at 0.7 MPa and 20 C (46 kg/m3) to simulate high pressure conditions of real multiphase transport systems; 0.102 Pa s viscosity oil and water as liquid phases. Two-phase and three-phase flow experiments were conducted at four liquid superficial velocities and different gas velocities for water cut values (The water cut is defined as the ratio between the superficial water velocity to the liquid superficial velocity).
The experimental results show that: The liquid fraction profile with a pure gas-oil shows higher values than for the three-phase flow profiles; the oil and water holdup profiles show water accumulation with respect of no-slip conditions due to more oil than water being entrained as droplets into the gas core; the three-phase pressure drop values are in between the gas-oil and gas-water values; when a comparison between the visual liquid heights with holdup measurements is made, there are indications that the shape of the gas-liquid interface may be curved. The application of gamma densitometry for measuring phase fractions in three-phase flows is shown and new data for systems using high viscosity oils for stratified-annular flows in horizontal pipes which is valuable for improving models and closures in multiphase flow simulators.