Optimization of a one-shot gamma densitometer for measuring area-averaged void fractions of gas-liquid flows in narrow pipelines

A novel theoretical method for optimization of a gamma densitometer was applied in measuring the area-averaged void fraction in gas-liquid flows. This theory provides design criteria that are comprehensive, mechanistic, quantitative and all are obtained from first principles. Also, a computer simulation was developed to test the design criteria and the predictions were compared with experimental data in the literature. Extensive experimental validation of the optimization theory was performed. Direct in situ measurement of void fraction using differential pressure, a double-sensor resistivity probe and lucite mock-ups were compared with the optimized gamma densitometer measurements. The results demonstrated good agreement between the reference measurements and the gamma densitometer in each case. The measured void fractions for the concurrent vertical forced flow ranged from 0.02 to 0.8, and spanned the bubbly, slug and churn turbulent flow regimes in a 25.4 mm tube. The mock-up studies used lucite tubes of 12.7 mm outer diameter as substitutes for the flow field over void fractions ranging from 0.03 to 0.8.