The performance of electromagnetic flowmeters in a liquid metal two-phase flow

Abstract

In order to investigate the characteristics of an electromagnetic flowmeter in a liquid metal two-phase flow, AC electromagnetic flowmeters were designed and manufactured. Two-phase flow experiments, encompassing bubbly to slug flow regimes, were realized with a water-air mixture and a liquid sodium-nitrogen mixture, respectively. The relation DeltaU(TP)=DeltaU(SP)/(1 -alpha), between the flow induced electromotive force (e.m.f.) of a single-phase flow and that of a two-phase flow, was verified by the measured e.m.f.s and the void fraction alpha for a bubbly flow regime. Whereas there is no difference in the shape of the flow induced e.m.f. between single-phase and bubbly flow, the signal amplitude of the bubbly flow is greater than that of the single-phase flow under the same water or liquid sodium flow rate, since the real liquid velocity is higher than that of the single-phase flow. In the case of a slug flow, the phase and the amplitude of the flowmeter output changed drastically when a slug bubble passed through the flowmeter. Therefore, the electromagnetic flowmeter shows good potential as a useful device for identifying the flow regimes. The void fraction in a bubbly flow can be measured using two electromagnetic flowmeters.