Calibration tests of pulse-Doppler flow meter at national standard loops

Calibration tests of UdFlow, the ultrasonic pulse-Doppler flowmeter manufactured by the Tokyo Electric Power Company, were conducted at the national standard loop in Mexico, CENAM (The Centro National de Metrologia), in order to evaluate the accuracy of the flowmeter. Four ultrasonic transducers were mounted circumferentially on the surface of 100 and 200 mm stainless steel pipes to measure four velocity profiles. Flow rates can be obtained by integrating each measuring line and averaging them. Air was injected upstream of the measuring point to provide bubbles as ultrasonic reflectors. Tests were conducted at five different flow rates with Reynolds numbers from 200,000 to 1,200,000. Tests were repeated six times at each flow rate to evaluate repeatability. In addition, a take-off and put-back test was carried out on the 100 mm pipe at a flow rate of 3000 L/min to evaluate reproducibility. The values of the CENAM loop are based on the average of weighing time while those of the ultrasonic-Doppler flow velocity-profile flowmeter are based on the time average of instantaneous values. The calibration tests found a deviation of less than 0.3% between the two devices in terms of the average of the values recorded in six rounds of measurement. Measurement at a different Reynolds number showed that the overall average deviation between the two devices was less than 0.3%.