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
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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