h1

TY  - THES
AU  - Gopala Krishna Moorthy, Vijaya Kumar
TI  - CFD simulation of the interaction of buoyant flows with nuclear aerosols
PB  - Rheinisch-Westfälische Technische Hochschule Aachen
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2023-10153
SP  - 1 Online-Ressource : Illustrationen, Diagramme
PY  - 2022
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2023. - Cotutelle-Dissertation
N1  - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022. - Dissertation, IIT Madras, 2022
AB  - In a severe accident, the prevailing flow in a nuclear reactor containment is driven by buoyancy forces and determines the transport of hydrogen, steam, air, and radioactive fission products—noble gases and aerosol particles. Multiple interacting phenomena such as turbulence, steam condensation, radiation heat transport, and structure-gas heat transfer due to the thermal inertia of steel and concrete structures govern the containment flow. The noble gases and nuclear aerosols carry significant decay heat, which may affect the gas mixing by inducing local buoyancy forces. A previous Ph.D. research project at Forschungszentrum Juelich and RWTH Aachen University analyzed the impact of decay heat on the buoyant flow inside the small-scale DIANA facility (L ∼ 0.7 m) with a sophisticated Euler-Lagrangian approach. It was conclusive that the decay heat of aerosol particles influences the gas flow. However, it also became obvious that the Euler-Lagrangian approach is computationally cumbersome for further investigations on a technical scale. In order to further investigate aerosol transport and the effect of associated decay heat on application scale, in the present work, a “fast-running” CFD model is developed based on the Euler-Eulerian approach to simulate the gas-aerosol transport in a containment. The unsteady-RANS approach, based on the k-ω-SST turbulence model, and a suitable wall condensation model, treat the gas flow. A simplified Eulerian model—Mixture model—is used for treating the aerosol transport with the consideration of drag, inertia, buoyancy, thermophoretic, and diffusiophoretic forces. The evolution of particle size distribution due to hygroscopic growth in humid atmospheres is treated with the Lognormal model for technical scale applications. The CFD model is systematically validated against small-scale experiments and then against the technical scale THAI experiments (L ∼ 9 m and Volume ∼ 60 m3). For the first time, the aerosol transport and impact of aerosol decay heat on buoyancy-driven mixing processes in the THAI facility is analyzed with a CFD approach. The results show that the decay heat effect significantly impacts the gas mixing phenomenon. Furthermore, the model’s scalability to application scale is successfully demonstrated by simulation of the VANAM-M3 experiment (Volume ∼ 615 m3), which involves steam and hygroscopic NaOH aerosol injection followed by a distribution and depletion phase.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2023-10153
UR  - https://publications.rwth-aachen.de/record/972404
ER  -