| In the paper,experimental and numerical simulation studies of boron mixing and diffusion characteristic in single-phase water fluid of the downcomer in the nuclear reactor.Diffusion equation and Peclet number(Pe)which defines the contribution of convective and diffusional effects,was analyzed by the experimental parameters.Macro-transport of boron caused by flow behavior is primary while molecular diffusion can be ignored.So rhodamine B(RhB)diffusion can simulate boron diffusion.A test ontology with visualization performance has been designed and processed.Flowing loop and optical system has been designed and build,and then all the systems has been debugged.The jet mixing RhB flow into the ontology to simulate the process of boron diffusion in the downcomer.Calibration experiment has been done with injecting uniform concentration of dye,including the concentration of 0.009375mg/L,0.0125 mg/L,0.015625 mg/L and 0.01875 mg/L,used LIF technique.In order to the real-time monitoring of the concentration fields,ratio method and calibration method of point to point has been adopted to programmed and handle fluorescence image.By being compared of two methods from the visual quality of the concentration and deviating from the true value of error,it was known that calibration of point to point can be better to eliminate influence of optical path,concentration and phase interface.The jet with RhB flowed into the downcomer and mixed with the water without the dye.The experiment conditions including the flow rate of 0.5498m~3/h,0.7883m~3/h and 1.1056m~3/h and the height of horizontal section of 5cm above injection entrance,0cm and 5cm below injection entrance.The results show that the larger the flow injection,the more of the injection flow along the horizontal direction,the more uniform concentration distribution is,and the better mixing effect is.The flow rate,in other word,the horizontal velocity influence directly uniformity of concentration distribution.For different horizontal section,mixing degree of concentration distribution above injection entrance degree of mixing is worse,while mixing degree of concentration distribution below injection entrance is better.The concentration distribution is caused by diffusion of the vertical direction of mass force.Physical model based on the test ontology was build and hexagonal structured mesh was generated.Boundary conditions and initial conditions are same to the experiment.Species transport model is adopted.So the concentration distribution of boron can be simulated at various times.Numerical simulation results show that the boron concentration distribution and interval are similar to the experimental results from qualitative analysis and quantitative analysis.Thus the mathematical model coincides well with the experimental results and reflect the distribution characteristic of boron concentration to a large extent.Besides,the velocity field can be helpful to explain the boron concentration distribution well.In conclusion,laser induced fluorescence technique can be applicable to measure well whole field of boron concentration in the downcomer.Based on the method,boron diffusion and distribution can be analyzed qualitatively and quantitatively all the field.Besides,experiment results are good agreements with numerical calculation.So the technique can be able to provide full data validation for numerical calculation. |
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