Study on a Novel Sensor of Wetness Measurement in Water/Air Flows.

In view of the character that wetness measurement for steam is difficult and inaccurate, a novel sensor of wetness measurement for flowing wet steam is developed by making use of capacitance method based on the fact that the water and steam have great different permittivities. The sensor can be installed in the steam pipe directly, so the steam will flow through it with full flow rate. Therefore the error due to drawing steam sample inaccurately is eliminated. By means of this sensor, on-line measurement of the wetness of wet steam can be realized. Based on the fact that air and steam have almost same permittivities, the flowing wet steam is simulated by spraying water into air flow in the experiment. Experiment with the novel sensor of wetness measurement in water/air flows shows that the frequency output decreases as the absolute humidity of flowing wet air increases. The relationship between the absolute humidity of air and the relative frequency deviation are obtained from the experimental data and this result accords with the theoretic conclusion. The sensor can endure high temperature and high pressure and has preferable precision, so it can be used to measure not only the wetness of flowing wet steam in nuclear power plants but also the water content of solid materials on-line after precise calibration. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]