Measurement of local steam content by electric probe

A method was described for measuring the local vapour content in two-phase flows with an electric probe. To verify the reliability of the measurements, a concurrent photographic recording of the two-phase flow was carried out in the area occupied by the probe. The experiments were performed on a water-air mock-up of a power reactor channel cell. The probe, functioning according to the principle of electrical resistance, could be moved along to study the phase distribution in the channel section. The main measuring element of the circuit is a long line with distributed parameters (a coaxial cable some 50 m long) and a wave resistance of 75 ohm. The resonance resistance was achieved at characteristic frequences over the range of about 20 to 35 Mcps. A change in the conductivity of the two-phase medium at the point where the detector is placed as a result of a phase shift, leads to the carrier frequency modulating by amplitude. Separation of the effective signal from the high frequency oscillation of the circuit is accomplished with a conventional diode detector. Processing of the photographic records of the flow patterns was reduced to calculation of the mean radii of despersoids from the two axes. Processing of the tracing tapes consisted in measuring the half-widths of the pulse and obtaining frequency patterns of the electric-probe signal recorded. The noise level was about 6% of the maximum height of the amplitude. The figures show phase distributions in the channel section for some flow patterns, recording of the signal from the electric probe to locate its positions in the channel, as well as the relationship between the electric signal and the size of the bubble