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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

APPLICABILITY OF THE SECOND MOMENT CLOSURE MODELS FOR TURBULENT HEAT FLUX OF THE TURBULENT NATURAL CONVECTION IN A CONFINED CAVITY

Get access (open in a dialog) DOI: 10.1615/IHTC16.cov.024128
pages 2953-2960

Resumo

During severe accidents in nuclear power plants, the molten corium (nuclear fuel and structure materials) relocates into the lower head of reactor pressure vessel and form a molten corium pool with the internal heat generation due to the decay heat of radioactive fuels. In the pool, complex phenomena, i.e., turbulent natural convection, decay heat, crust formation along the boundary are involved and affect to evaluate the thermal loading to the reactor vessel. Turbulent natural convection is one of the major phenomena which determines the thermal behavior of the molten pool. In the real reactors, a high modified Rayleigh number (~1018) is expected, which means natural convection with strong turbulence. It has been known that the eddy diffusivity model for turbulent heat flux has a limitation to simulate the buoyancy dominant flow.

In this study, the second-moment closure models for turbulent heat flux are employed, and the models are validated with King's DHC and SIGMA-RP. It is observed that algebraic heat flux model can predict anisotropic turbulent heat flux and the Nusselt number behavior, while eddy diffusivity model fails. Characteristics of natural convection with decay heat are analyzed: the effect of the advanced model on the Nusselt number behavior compared to the eddy diffusivity model and the effect of Prandtl number on the overall heat transfer.