Nuclear magnetic resonance (NMR) two-phase mass flow measurements

Abstract An NMR measurement method for highly-turbulent liquid-gas two-phase flow 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 (eds J.M. Delhaye and G. Cognet). Springer, Berlin, 1984, p. 435]. It allows measurement of the liquid velocity and of the fraction, both averaged over the inner volume of the NMR RF coil and over the measuring time. By signal-averaging, it is possible to extend the averaging time to mins, or even hrs or days. This time-averaging improves the signal relative to background noise as well as to fluctuations caused by the flow and hence improves the accuracy of the measurements. The influence of insufficient mixing of the spins during the polarization period is discussed. Measurements with this method have been executed in turbulent water flow and in water-nitrogen two-phase flow. The calibration procedure for the velocity v NMR and liquid fraction ϵ NMR is done with turbulent water all-liquid flow. The velocities ranged from 0.1 to 5 m/s and the liquid fraction from ca 0.5 to 1.0. The mass flow MF NMR in two-phase flow, which is proportional to the product v NMR times ϵ NMR , indicates an accuracy of better than /t+-5%.