Two-Phase Flow Measurement With Orifices

This paper presents a practical method for computing two-phase flow rates through AGA-ASME stamdard orifice meters to a tolerance of 1.5 per cent. A rational equation is developed modifying the present single-phase metering equation by the introduction of one experimentally determined constant and permitting the use of data already contained in the ASME Fluid Meters Research Committee publications. Equations are also given for computing the two-phase flow of natural gas using the American Gas Association Report No. 3. No additional data are needed for the solution of two-phase flow metering problems. The experimental constant is derived from the analysis of 90 test points for two phase flow of steam-water, air-water, natural gas-water, natural gas-salt water, and natural gas-distillate combinations. Three separate test series are described for orifices equipped with radius, flange, and pipe tap locations in 2 1/2, 3, and 4-inch pipe with beta ratios ranging from 0.25 to 0.50. Pressures ranged from atmospheric to 920 psia, differentials from 10 to 500 inches of water, and liquid weight fractions from 2 to 89 per cent. Temperatures were from 50 to 500 F and Reynolds numbers for the liquid from 50 to 50,000 and for the gas from 15,000 to 1,000,000. These data were correlated to a standard deviation of 0.75 per cent. The areas where further research is needed to increase the universality of the two-phase metering equation are delineated.