Experimental Research On Void Fraction Distribution Of Vapor-water Two-phase Flow In Vertical Tube Bundles

The steam generator is an indispensable equipment in the nuclear boiling water reactor system.Second primary side bundle between gas-liquid two-phase flow status of the research related to the stability of the nuclear power plant in operation.Void fraction is an important parameter in the study of boiling heat transfer and flow characteristics of gas-liquid two-phase flow.It is an pivotal indicator to distinguish the difference between two-phase flow and single-phase flow,and its data plays an indispensable role in two-phase average density calculation,pressure drop calculation and flow pattern analysis.In the present paper,the tube bundle of steam generator heat exchanger was used as the prototype to design the experimental section tube bundle.Meanwhile,a set of high-temperature and high-pressure steam-water two-phase measurement system had been reformed.The experimental pressures were 5 MPa,7 MPa,9 MPa,respectively,the mass flow was 550,1100,1700kg/h,and the thermodynamic vapor quality ranged from 0.003 ?0.4.The relative uncertainty of measured and calculated parameters is within 0.47%-6.75%.In order to obtain the distribution of vapor-water two-phase void fraction between bundles,the local void fraction was obtained by inserting the optical fiber probe into the central point of the bundle.The bundle area was divided into seven measuring positions by gamma ray,and the line void fraction distribution at each location was obtained.From this,the average cross-section void fraction of the bundle section was calculated.At the same time,the influence of pressure and mass flow rate on the void fraction of average cross-section was analyzed,and the size relationship of the three under typical working conditions was drawn.In this paper,seven groups of commonly used empirical correlations of void fraction were selected to predict the distribution of void fraction between bundles.By comparing with experimental data,the reliability and accuracy of the experimental system were verified.Combining Armand's formula theory with the experimental data,a new calculation correlation was obtained,which was suitable for the experimental conditions in this paper.The calculation correlation is in good agreement with the previous research data under different experimental conditions,and the deviation is less than 15%.This study is of great significance to the structure design and flow characteristics of steam generator.