NUCLEAR-MAGNETIC-RESONANCE (NMR) 2-PHASE MASS-FLOW MEASUREMENTS

An NMR measurement method for highly-turbulent liquid-gas two-phase fl ow has been developed in this laboratory [Kruger, G.J., Haupt, J. and Weiss, R. A nuclear magnetic resonance method for the investigation of two-phase flow. In Measuring Techniques in Gas-Liquid Two-phase Flows leds J.M. Delhaye and C. Cognet). Springer, Berlin, 1984, p. 435]. It allows measurement of the liquid velocity and of the fraction, both a veraged over the inner volume of the NMR RF coil and over the measurin g time. By signal-averaging, it is possible to extend the averaging ti me to mins, or even hrs or days. This time-averaging improves the sign al relative to background noise as well as to fluctuations caused by t he flow and hence improves the accuracy of the measurements. The influ ence of insufficient mixing of the spins during the polarization perio d is discussed. Measurements with this method have been executed in tu rbulent water flow and in water-nitrogen two-phase flow. The calibrati on procedure for the velocity v(NMR) and liquid fraction epsilon(NMR) is done with turbulent water all-liquid flow. The velocities ranged fr om 0.1 to 5 m/s and the liquid fraction from ca 0.5 to 1.0. The mass f low MF(NMR) in two-phase flow, which is proportional to the product v( NMR) times epsilon(NMR), indicates an accuracy of better than +/-5%. C opyright (C) 1996 Elsevier Science Ltd.