TWO-PHASE ANNULAR FLOW IN A VERTICALLY MOUNTED VENTURI FLOW METER

In the present research work, the experimental investigation of a vertical upward annular two-phase flow in a Venturi Flow Meter (VFM) is performed. The pressure drops between the inlet and throat section and between inlet and outlet (irreversible pressure drops) are measured and analyzed. The flow meter is characterized by an inlet diameter of 80 mm and a throat diameter of 40 mm (β=0.5), with equal convergent and divergent angles (θ=21°). The instrument has been tested in a test section, having an internal diameter (Di) of 80 mm and a total length (L) of about 4 m, with air-water two-phase flow at ambient pressure. The air superficial velocity ranged between 14 and 18 m/s while the water superficial velocity ranged between 0.0008 and 0.005 m/s, so that the flow pattern was annular and the corresponding void fraction was higher than 0.97, while the flow quality ranged between 0.78 and 0.96. The dependency of the pressure drops on the phases velocities has been analyzed and modeled as a function of the superficial velocities of the phases. In addition the possibility to derive the mass flow rate of the two-phases from the sensor signals, when the flow pattern does not change, has been analyzed. The developed model allows the evaluation of the flow quality of the mixture with an accuracy of 5% and the estimation of the mass flow rate of air and water with an accuracy of 2% and 30% respectively.