Development Of A Conductivity Probe Measurement System And Study On Two-phase Characteristics Of ERVC Channel

Two phase flow widely exists in nuclear energy,aerospace,petroleum,refrigeration and many other fields.Because of the uncertainty of the interaction between phases,two-phase flow has more complex flow and heat transfer characteristics than single-phase flow.In view of the complex characteristics of two-phase flow,it is of great significance to accurately measure the void fraction,interface velocity and other two-phase flow parameters for the study of two-phase structure and the law of two-phase flow change.The invasive conductivity probe is one of the most effective two-phase flow measurement methods because of its high accuracy,good economy and wide application.In this paper,the conductivity probe measurement system is designed and manufactured,and applied to the study of two-phase characteristics of ERVC test loop.According to the principle of conductivity probe measuring two-phase flow parameters,this paper developed four electrode array probe,four electrode conductivity probe and corresponding signal acquisition device,and developed a signal processing program.By setting up a calibration bench,the measurement results are compared with the results of high-speed photographic analysis,and the void fraction,interface velocity and interface area concentration measured by the probe are calibrated respectively.The calibration results show that the measurement error of the probe for phase interface velocity and interface area concentration is less than 15%,the measurement uncertainty of void fraction is 3%,and the effective bubble response time is 0.01s.It has high measurement accuracy and response characteristics and can be further used in the parameter measurement of ERVC experimental research.External cooling of pressure vessel is one of the important mitigation measures for severe accidents of large-scale advanced PWR nuclear power plant.The two-phase characteristics of coolant in the flow-path is the difficulty in the research of ERVC.In this paper,the RELAP5 numerical simulation and experimental measurement methods are used to carry out comparative study.The experimental measurement was carried out in the large-scale IVR-ERVC engineering verification test device REPEC-Ⅱ.In this paper,a probe measurement system was developed to measure the void fraction in the ERVC channel.The experimental results show that the average void fraction of each inclined position in the arc section of the test body increases with the increase of heating power,and decreases from near to far away from the wall in the radial direction,and increases with the increase of the inclined angle along the flow direction.The thickness of two-phase boundary layer in ERVC channel increases with the increase of inclination angle and local heat flow.When the local heat flux exceeds1000k W/m~2,the thickness exceeds 100mm.In addition,the flash phenomenon at the outlet of the riser will cause periodic oscillation of the flow and pressure of the loop,resulting in flow instability.The results of numerical simulation for the radial distribution of void fraction and flash phenomenon in the heating channel are basically consistent with the experimental results.In this paper,a conductivity probe measurement system for two-phase characteristics measurement in ERVC flow channel is developed and the calibration of relevant measurement parameters is completed.It is further applied to IVR-ERVC large-scale engineering verification test device.In this paper,the measurement and analysis of the two-phase characteristics in ERVC flow channel are preliminarily completed,and the physical phenomena and distribution rules of the two-phase characteristics under ERVC conditions are obtained,which provides a basis for the subsequent development of CHF mechanism model in IVR-ERVC.