An experimental study on installation effects of pipe elbow on the electromagnetic flowmeter characteristics (turbulent flow)

An ElectroMgnetic Flowmeter(EMF) essentially averages the velocity distribution over the pipe cross-sectional area, and the measured value is dependent on the velocity profiles. In this study, installation effects of 90 deg. long elbow(KS B 1522, ISO 3419) on the EMF characteristics was investigated. A commercial EMF was adopted and the distribution of magnetic field in the electrodes cross section was measured. In the experiment, the national flow standard system, of which measurement uncertainty was evaluated in a accordance with ISO 17025 recommendation, was used for characterization of EMF. The leading line has 150D long straight pipe to established a fully developed flow before entering into the elbow and the elbow was installed downstream of it, then the flowmeter was tested within 50 D from the elbow. The installation effects of the flowmeter were investigated by varying the mean velocity(Reynolds No.)in pipe section, the locations and the direction of electrodes plane.(φ) From the experimental results, we find the optimal conditions to get most accurate measurements. Generally, the deviations from the calibration value were less than 0.5 % in farther than 10D distance from the elbow and the direction of electrodes plane, φ =90 deg. yielded the smallest measurement deviation. These characteristics were shown consistently in turbulent region regardless of the mean Reynolds number