Award Date

5-1-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Committee Member

Yi-Tung Chen

Second Committee Member

Brendan O'Toole

Third Committee Member

Hui Zhao

Fourth Committee Member

Jaeyun Moon

Fifth Committee Member

Jichun Li

Number of Pages

152

Abstract

This dissertation is a study of material corrosion, along with solving momentum, energy, and mass transport equations by using the Lattice Boltzmann method (LBM) for the mesoscale modeling of oxygen transfer in liquid metals within a non-isothermal domain. One of the main goals of the project, proposed by the U.S. Department of Energy (DOE), is to control and decrease the corrosion of materials, which are often a common problem in advanced nuclear reactors and accelerator driven systems (ADS). One of the most efficient ways to decrease the corrosion rate is to add oxygen to the coolant to create an oxide layer, which it can act as a shield over the contact surface. The concentration of oxygen is the key in creating an effective protective layer. In the associated tasks spanning throughout this project, liquid lead and lead-bismuth eutectic (LBE) have been selected to serve as liquid metal coolants because of their suitable physical properties like high heat capacity, high thermal conductivity, high boiling point, low melting point, and low vapor pressure. Specifically, LBE is chemically safe in contact with water or moist air. However, the corrosiveness of lead and lead alloys has put a huge limitation on their applications in the nuclear industry.

The LBM was the basis for the numerical modeling, which includes momentum, energy and mass transport of turbulent flow associated with dissolution of steel, the growth of oxide layer, low Prandtl (Pr) fluids, and inherently slow corrosion process. Generally, the LBM solves the fluid problem in mesoscale, limited to the incompressible fluid only. However, several research works have improved this method to include multiphase flow, turbulent problems, particulate flows, and supersonic flow phenomena. In the present study the new development of Double multi-relaxation time model has been accomplished, which can stabilize the numerical simulation in turbulent regions, to couple heterogeneous chemical reactions at the surface and account for corrosion and oxide layer growth.

The study of oxygen distribution in the LBE flow in the presence of nano particles and under magnetic field comprises the first and second objectives of this dissertation, respectively. An improvement in oxygen distribution for the LBE system has been achieved by adding nano particles to the base fluid. The results indicate that oxygen diffuses throughout the coolant faster, which results in lower equilibrium time for the LBE system. The magnetic force effect on the oxygen distribution is also a focus of this study. The results show that the magnetic field would be a barrier for oxygen transfer in an LBE system and would increase the equilibrium time. On the other hand, different flow patterns occurred by applying different magnetic force magnitudes. A certain flow pattern can deliver oxygen more efficiently to the exposed surfaces than other flow patterns. Finally, a Double multi-relaxation time model (Double-MRT) has been developed to couple with the reactive boundary condition to study steel corrosion in LBE flow, because the single-relaxation time (SRT) or multi-relaxation time (MRT) LBM models present numerical instability in dealing with turbulent low Prandtl number liquid flows. The obtained numerical results were benchmarked with experimental data and good agreement has been achieved. The developed Double-MRT model is a robust, efficient, and accurate computational tool to determine steel dissolution and precipitation of the oxide layer related to corrosion in advanced nuclear reactors.

Keywords

Corrosion; Lattice Boltzmann Method; Lead-bismuth eutectic

Disciplines

Engineering

File Format

pdf

File Size

6.2 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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