The Effect of Elbows on the Accuracy of Liquid Flow Measurement with an Insertion Flowmeter

摘要

The measurement error of an insertion flowmeter located downstream of a 90-degree elbow was quantified for water flowing in 4 in. (0.10 m) and 6 in. (0.15 m) diameter pipes. The flowmeter location was varied between 2 and 9 diameters downstream of the elbow. Three metering angle orientations relative to the outside horizontal plane of the elbow were evaluated: 0, 90, and 180 degrees. Three radii of curvature were also evaluated: 2.5 in. (0.06 m), 4.5 in. (0.11 m), and 6.5 in. (0.17 m). For a 4 in. (0.10 m) diameter pipe with a radius of curvature of 2.5 in. (0.06 m), the largest measurement error was 28% at 2 diameters downstream of the elbow and 180-degree orientation. For a 4 in. (0.10 m) diameter pipe with a radius of curvature of 4.5 in. (0.11 m), the largest measurement error was 15% at 2 diameters downstream and 180-degree orientation. For a 6 in. (0.15 m) diameter pipe with a radius of curvature of 2.5 in. (0.06 m), the largest measurement error was 45% at 2 diameters downstream and 180-degree orientation. The length required for measurement error to be less than 5%for4in. (0.10 m) and 6 in. (0.15 m) diameter pipes ranged from 6 to 10 diameters downstream of the elbow.