자료유형  

 학위논문

Control Number  

0017162822

International Standard Book Number  

9798382739489

Dewey Decimal Classification Number  

620

Main Entry-Personal Name  

Mao, Jiaxin.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of Michigan., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

199 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

General Note  

Advisor: Manera, Annalisa;Petrov, Victor.

Dissertation Note  

Thesis (Ph.D.)--University of Michigan, 2024.

Summary, Etc.  

요약The High-Temperature Gas-cooled Reactor (HTGR), one of the six candidates for the advanced nuclear reactors in the Generation IV International Forum (GIF), has received great attention due to its enhanced safety, high thermodynamic efficiency, and suitability as energy source for high-temperature industrial processes such as hydrogen production. However, despite extensive advances in the development of this design, there remain thermal-hydraulic challenges that need to be addressed before commercialization.One challenge is the measurement of the primary coolant flow. Currently, the primary helium coolant flow is not directly measured but rather inferred from either the energy balance of the turbine compressor or the helium circulator rotational speed. Though functional, both methods introduce large uncertainties; therefore, HGTR operation would benefit greatly from the development of a suitable gas flow meter. Such development is challenging due to the high flow rates (the gas velocities are in the range of 10 − 15 m/s at the nominal operating conditions), high operating temperatures ( 700oC), and high neutron flux and gamma fields in the reactor core. No commercially available flow meters are suitable for flow rate measurements in such a harsh environment.Another challenge is related to the accurate prediction of the plant behavior during an extended Loss of Force Circulation (LOFC) accident, one of the Design Basis Accidents (DBAs) that have to be considered when licensing the design. During LOFC scenarios, the flow in the reactor pressure vessel reverts its direction, moving upwards. The extent to which the hot coolant jets exiting the core mix in the upper plenum will determine the heat removal rate, the occurrence of local hot spots, and the potential for thermal striping. In severe cases or after repeated cycles, the striping can thermally fatigue the material of the upper plenum internals, leading to component failure. While 3D Computational Fluid Dynamic (CFD) models can be useful for an accurate prediction of thermal mixing and the occurrence of hot spots in the HTGR upper plenum, a shortage of high-resolution experimental data has hampered the validation of such models.This thesis addresses the challenges mentioned above by 1): designing a novel acoustic flow meter and 2): conducting high-resolution experiments for mixing in large enclosures to establish a high-resolution database specifically designed for the validation of high-fidelity CFD models. The novel acoustic flow meter relies upon the principle of vortex-induced acoustics. Within the present dissertation, a combination of experiments and simulations was conducted to support the development and optimization of the flow meter design and to successfully demonstrate its proof of principle. To investigate the flow conditions relevant to mixing in the upper plenum and establish a database for CFD model validation, two experimental facilities were designed and constructed at the University of Michigan. Special care was dedicated to guaranteeing well-characterized boundary conditions, so that the data could be used for the validation of CFD codes. First, the Michigan Multi-jet Gas-mixture Dome (MiGaDome) facility, a 1/12th scaled down from the upper plenum geometry of the Modular HTGRs design, was designed and built within the workscope of the present dissertation to investigate multi-jet interactions in a domed enclosure using optical measurements such as Laser Doppler Velocimetry (LDV) and Particle Image Velocity (PIV). Second, the High-Resolution Jet (HiRJet) facility was used to investigate the propagation of stratified fronts in a body of fluid. Wire-Mesh Sensor (WMS) units were used for high-resolution measurements of the time-dependent density field and characterization of the stratified front. High-resolution experimental data measured at these two facilities were used to shed light on the flow mixing in large enclosures with or without the presence of stratified density fronts. Extensive code validation has been conducted for RANS based turbulence models to assess and improve the performance of the computational models. The work in this thesis is expected to benefit the advancement of HTGR designs by providing practical solutions and through enhanced computational tools.

Subject Added Entry-Topical Term  

Engineering.

Subject Added Entry-Topical Term  

Nuclear engineering.

Subject Added Entry-Topical Term  

Fluid mechanics.

Subject Added Entry-Topical Term  

Computational physics.

Index Term-Uncontrolled  

Thermal fluids

Index Term-Uncontrolled  

High-Temperature Gas-cooled Reactor

Index Term-Uncontrolled  

Computational Fluid Dynamic

Index Term-Uncontrolled  

Flow instrumentation

Index Term-Uncontrolled  

Mixing in large enclosures

Added Entry-Corporate Name  

University of Michigan Nuclear Engineering & Radiological Sciences

Host Item Entry  

Dissertations Abstracts International. 85-12B.

Electronic Location and Access  

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Control Number  

joongbu:658637