Study On The Uncertainty Qualification For CFD Simulation Of Single-Phase Flow And Heat Transfer In Rod Bundles

With the development of Computational Fluid Dynamics(CFD)and the rapid improvement of computer performance,CFD has been applied widely in the nuclear industry.Nuclear fuel assembly is the core component of nuclear reactor.Computational fluid dynamics(CFD),as an simulation tool,is widely used in the flow and heat transfer analysis of rod bundles.On the one hand,there are different opinions on the application of the CFD methods to rod bundles.There are different best practices guidelines for CFD application from various institutions.As a result the CFD simulation credibility is controversial.On the other hand,CFD analysis is based on deterministic conditions,e.g.deterministic boundary and initial conditions.In the reality,however,these conditions contain large uncertainty,which will challenge the credibility of the simulation results.Considering the fact that traditional uncertain analysis methods,such as Monte Carlo sampling,are not applicable to the uncertainty analysis of CFD simulation because of its huge amount of calculation effort,the aim of this paper is to find a new method to do the uncertainty quantification of the CFD simulation.For the purpose of this thesis,the experimental flow measurements in a 4x4 rod bundle performed in the Korea Atomic Energy Research Institution(KAERI)are taken.CFD simulation of flow in the 4x4 rod bundle is carried out with the effect of grid,turbulence model and wall treatment.Based on the comparison of the experimental data with the CFD simulation results,,the best practice method of CFD simulation on the single-phase flow and heat transfer in rod bundle is conducted,and the sensitivity coefficient method is created.This paper focuses on both the effect ofkon pressure drop and the effect ofs_t on heat transfer coefficient.The results show that the predicted uncertainty for pressure drop is 108.72Pa and the uncertainty for heat transfer coefficient is 973.76W/K×m~2.