Gas Fraction Measurements using Single and Dual Beam Gamma-Densitometry for Two Phase Gas-Liquid Pipe Flow

Gamma-densitometry is a widely used non-intrusive measurement technique to measure the local gas fraction of gas-liquid two-phase pipe flow. The ability to accurately predict the gas fraction of gas-liquid pipe flow is of great importance in many process industries, e.g. in the oil and gas industry. The objective of this work has been to study different gamma-ray beam trajectories for single and dual beam gamma-densitometers in order to determine the optimal source-detector layout of a dual beam densitometer for vertical gas-liquid pipe flow. The work is based on experiments using a high-speed gamma-ray tomograph (GRT) designed and prototyped at Department of Physics and Technology, University of Bergen. The GRT, which was originally developed for imaging of multiphase hydrocarbon flow, is based on 85 independent gamma-ray beams. Each beam represent an individual single beam densitometer measurement. Combined, the 85 beams accurately measures the density or cross sectional fractions of two-phase flow. The experimental work was conducted using the multiphase flow facility at Christian Michelsen Research, Norway. The results of the experiments show which beam trajectories gives the best accuracy for single and dual beam gamma-densitometer measurement.