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The Effect of a 90 Degree Elbow on the Accuracy of Liquid Flow Measurement with an Insertion Flowmeter
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To quantify the measurement error of slow meters in the developing length, simulation model development, local velocity measurements, flowmeters test, and regression model development were carried out for 10.2 cm, 15.2 cm, and 20.3 cm pipe system. The test facility used was the flow loop at Riverside campus, Texas A&M University. The test section was made on the basis of ASME guidelines (1971). Simulation models were developed using Fluent/UNS to estimate the velocity contours in the developing length of 10.2 cm, 15.2 cm and 20.3 cm. for evaluation of the standard deviation and the non-dimensional velocity contour data, the developing length of 10.2 cm, 15.2 cm, and 20.3 cm pipe with pressure fitting 9short radius of curvature) was 6 diameters downstream. For 10.2 cm with a long radius of curvature elbow, it was 10 diameters downstream of the elbow. The local velocity at 2 and 9 diameters downstream was measured with the help of a five0hole probe. The distorted velocity profile was distorted to the outside of pipe at 2 diameters downstream and 0 degrees. It had a double peak at 90 degrees and 2 diameters downstream. For 10.2 cm with a pressure fitting, the developing length was 6 diameters downstream. On the other hand, it was 9 to 10 diameters for 10.2 cm with the long radius of curvature. For 10.2 cm and 15.2 piping system with pressure fittings, the largest measurement error was -25% and -40% at 2D and 180 degrees. On the other hand, for the 102 cm pipe with R = 11.4 and 16.5cm, the largest measurement error was -15% at 2D and 180 degrees. The measurement error decreases exponentially or quadratically. Finally, regression models were developed on the basis of the data trends of simulation, five-hole, and flowmeters data. The measurement error of simulation results, five-hole, and flowmeters data decreased quadratically or exponentially in the developing length. Exponential model was well described in the re0developing and fully developing region for 0 and 180 degrees flowmeters orientation. On the other hand, the data at 90 degrees was fluctuating and converging at zero. .
Woo, Seongwoo (2000). The Effect of a 90 Degree Elbow on the Accuracy of Liquid Flow Measurement with an Insertion Flowmeter. Energy Systems Laboratory. Available electronically from