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Similarity model for estimating the error of clamp-on ultrasonic flowmeter: Flow in water supply piping system
Author(s)
Wachirapunyanont, Rathachot
Siriparinyanan, Pontakorn
Date Issued
January 1, 2017
Type
Article
Abstract
This study was aimed at presenting the similarity model for the estimation of error of a clamp-on, transit-time ultrasonic flow measurement. Dimensional analysis was based on the Buckingham Pi’s theorem. The groups of independent parameters that were taken into account for the analysis included pipe characteristic, fluid characteristic, and meter installation setting. Experimental testing section was fabricated using PVC pipes with diameters of 1-in and 2-in and 45º PVC elbows. Flow velocity was fixed at 0.5 m/s. The upstream and downstream distances were in the ranges of 2D-20D and 2D-10D, respectively. It was found that the upstream and downstream distances greatly affected the accuracy of the measurement. Larger relative errors were found from the measurement on the smaller pipe. With the installation of ultrasonic transducers according to the recommended value by FCI, the error obtained with the measurements on 1-in and 2-in diameter pipes were, respectively, 7% and 0.35%. The acceptable measurement ranges of upstream distance for 1-in and 2-in diameter pipes were 16D-20D and 6D-20D, respectively. The measurements on a 2-in diameter pipe with a downstream distance in a range of 4D-10D was acceptable. For the 1-in diameter pipe, any downstream distance less than 10D resulted in unacceptable error. The accuracy of measurement was more sensitive to the change of downstream distance than the change of upstream distance. The applicable range of the prototype prediction equation was greatly affected by the flow model. The equation obtained with a 1-in diameter flow model could only be used to predict a 2-in diameter prototype within a range of 18D-20D. Increasing the size a flow model could greatly broaden the applicable range the applicable range of the prediction equation. A 2-in diameter flow model could be used to predict a prototype upto 150 in.
Citation
Engineering Letters, 25(3), 239-246, 2017