Measurement and Simulation of the Turbulent Dispersion of a Radioactive Tracer in a Two-Phase Flow System


Measurement and Simulation of the Turbulent Dispersion of a Radioactive Tracer in a Two-Phase Flow System

Rohde, U.; Hensel, F.

Studies of the turbulent dispersion of a radiotracer in an experimental setup with natural convection liquid­gaseous flow were carried out. In a series of experiments, a liquid­gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water, or by catalytic disintegration of H2O2. A small amount of a positron emitting radiotracer liquid was injected instantaneously at a certain point of the tank. The Positron Emission Tomogaphy (PET) technique was used to observe the spreading of this tracer liquid in the bubbly flow. For that case a double head gamma detector array was used for measuring the positron annihilation rate which is proportional to the tracer concentration. From the experimental data the dispersion coefficient D for the tracer liquid was calculated, assuming an isotropic spreading of the concentration profile after separation of the linear displacement of the maximum concentration point.
Calculations for this two­phase flow with spreading tracer were carried out for selected experiments with air injection into water using the computational fluid dynamics code CFX­4.3. Here, the Euler­Euler continuum approach using a homogeneous low Reynolds number K,epsilon­model was applied. The evolution of the bubble size distribution (coalescence and break-up of the bubbles) was taken into consideration. A reasonable agreement was achieved between calculated and measured values of the turbulent dispersion coefficient D. A nearly linear correlation between the gas superficial velocity vgas and D was found in agreement with other authors.

Keywords: radioactive tracer; positron emmission tomography; two-phase flow; turbulent dispersion; CFD simulation

  • Poster
    5th German-japanese Symposium on Bubble Columns, May 28 - 30, 2000, Dresden Proc. pp. 235-240
  • Contribution to proceedings
    5th German-japanese Symposium on Bubble Columns, May 28 - 30, 2000, Dresden Proc. pp. 235-240

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Publ.-Id: 3286