On the measurement of the mass flow rate of horizontal two-phase flows in the proximity of the transition lines which separates two different flow patterns

A venturi nozzle coupled with a capacitive holdup meter was tested to measure the gas–liquid mass flow rate. An experimental facility was built and operated with air–water mixtures. It had a straight horizontal Plexiglas pipeline, 13 m long, and 34 mm internal diameter, and could produce several air–water flow patterns, comprising the stratified smooth, stratified wavy and slug flows. The gas–liquid mass flow rate was computed from the pressure difference measured, between the venturi taps and the liquid holdup in the capacitive meter, through 3 alternative procedures. The results showed that their application depended on the flow pattern and on the correlations used to calculate the flow quality and the mixture density.Water accumulation was observed in some tests between the holdup meter and the Venturi, trapped during the interval between two succeeding water slugs by the venturi’s throat reduced cross sectional area. This flooding effect can cause an error in the flow holdup measurement and, consequently, in the gas–liquid mass flow rate. A correction methodology was proposed.