Doctoral Dissertations

Abstract

This comprehensive study investigates the thermal-hydraulic mechanisms and convective heat transfer characteristics within (PWRs), with a focus on (SMRs) under both single-phase and two-phase bubbly flow conditions. Specifically, the research investigates the complex bubble dynamics in two-phase flow rod bundles, which are crucial for understanding reactor behavior during loss-of-coolant accidents (LOCA). Employing an advanced experimental setup developed at the (mFReel) at MST, this work measures critical parameters such as void fraction, bubble passage frequency, bubble velocity, bubble chord length, and interfacial area concentration (IAC) using a four-tip optical probe across various locations in the rod bundle. The findings reveal that the distribution of void fraction and IAC is significantly influenced by the superficial inlet liquid velocity, with the bubble breaking and swirling effects of mixing vane spacer grids (MVSGs) playing a dominant role in the observed phase distribution changes. Additionally, the research provides a detailed mapping of heat transfer coefficients, highlighting the impact of two-phase flow dynamics on thermal hydraulics within the reactor core. The presence of air-water two-phase flow, as encountered during LOCA events, necessitates a reevaluation of existing models and correlations for convective heat transfer. By integrating measurements of bubble dynamics with convective heat transfer analysis under the influence of MVSGs, the study offers a novel insight into the interplay between flow dynamics and heat transfer in nuclear reactor settings. The results not only contribute to enhancing reactor safety and performance but also provide valuable data for developing more robust heat transfer correlations and benchmarking computational fluid dynamics (CFD) models.

Advisor(s)

Al-Dahhan, Muthanna H.

Committee Member(s)

Alajo, Ayodeji Babatunde
Alnaseri, Hayder
Schlegel, Joshua P.
Albarqi, Mubarak
Usman, Shoaib

Department(s)

Nuclear Engineering and Radiation Science

Degree Name

Ph. D. in Nuclear Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2025

Journal article titles appearing in thesis/dissertation

This dissertation consists of the following three articles, formatted in the style used by the Missouri University of Science and Technology:

Paper I, found on pages 18–79, ready to submit it to Applied Thermal Engineering Journal.

Paper II, found on pages 80–121, ready to submit it to Annals of Nuclear Energy Journal

Paper III, found on pages 122–184, ready to submit it to Progress in Nuclear Energy Journal.

Pagination

xvi, 190 pages

Note about bibliography

Includes_bibliographical_references_(page 189)

Rights

© 2025 Saud Aldawood , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12494

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