Experimental evaluation of ISA 1932 nozzle for differential pressure measurement in air–water two-phase flows

Accurate measurement of multiphase flows remains a significant challenge because of complex phase interactions and flow-regime variability. This study investigates the use of an ISA 1932 nozzle for differential pressure-based measurement of air–water two-phase flows. The test object was an ISA 1932 nozzle compliant with the PN-EN ISO 5167-3:2005 standard. A dedicated experimental test rig was developed to enable precise control of water flow rates and air injection. Tests were conducted with two fixed air mass flow rates (1.0690 kg/h and 0.6485 kg/h) and varying water flow rates up to 35 m³/h. The resulting flow characteristics exhibited strong power-law correlations with R² values exceeding 0.999 for both test series. The average discharge coefficient Cavg for the two-phase mixture was determined to be 0.9622, remained within a ±1.5% tolerance across a Reynolds number range of 50,000 to 200,000. The findings confirm that the ISA 1932 nozzle is a reliable and accurate device for measuring two-phase air–water flows under controlled conditions, providing a cost-effective alternative to more complex measurement technologies.