Flow rate and uncertainty calculation theory for transit time ultrasonic flowmeter

Flow rate and uncertainty calculation for transit time Ultrasonic Flow Measurement Systems (UFMS) for NPPs are developed in this work. Feedwater of NPP has characteristics of high Reynolds number, high temperature, and high pressure. Therefore, accurate measuring of feed water is required to reduce the uncertainty which occurs during installation, measuring and data processing. We classify the uncertainty factors as; velocity profile correction factor, diameter measurement of pipe inside diameter, spacing between transducers and the density of fluid. Uncertainty calculations were done using feed-water pipe data and plant operating data. For verification of the calculation results, the experiments under standard fluid loop were taken place. The discrepancy between known mass flow rate and the measuring flow rate is approximate 0.6%. It shows a good agreement with the theoretical uncertainty of 0.52%