Author ORCID Identifier
https://orcid.org/0000-0002-2331-7882
Defense Date
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Mechanical and Nuclear Engineering
First Advisor
Lane Carasik
Second Advisor
Karla Mossi
Third Advisor
Thomas Roper
Fourth Advisor
Floren Rubio
Fifth Advisor
Cody Wiggins
Abstract
The development of clean energy systems is paramount to reducing mankind's climate impact. These clean energy systems include solar, wind, and nuclear power where nuclear power shows a reduced lifetime carbon dioxide footprint per kilowatt hour compared to other sources [102]. Advanced nuclear reactors, fusion energy systems, and concentrated solar power designers are looking at using molten salt heat transfer fluids and improved heat exchanger design to increase power production and efficiency of clean energy systems. The improving heat transfer within the main heat transfer components within advanced nuclear reactors will enable increased efficiencies and power production.
Heat transfer improvements within the heat transfer components of these reactors can be achieved through either passive or active enhancements where active enhancements require an external source and passive consist of geometric changes [85,15,11]. In particular, this work will focus on twisted elliptical tube passive heat transfer enhancements. These heat transfer enhancements show improved heat transfer, minimal increases in pressure drop, develop self-supporting structures, and show improved vibrational resistance [66,8, 63, 127, 151, 38, 14, 129, 29, 34, 77, 126, 54, 153]. Previous investigations into twisted elliptical tubes found that the inclusion of twisted elliptical tubes shows improved thermal performance when compared to traditional straight tubes for similar conditions. Unfortunately, literature is limited in corresponding Prandtl ranges and current correlations show substantial disagreements [66, 8, 63, 127, 151, 38, 14, 129, 29, 34, 77, 126, 54, 153]. Correspondingly, previous computational fluid dynamics (CFD) simulations have shown improved thermal performance in twisted elliptical tube geometries is likely due to the swirling of the tubes. Although, there exists a lack of experimental studies in these geometries to compare with CFD simulation for validation efforts [29, 34, 77, 126, 54, 153]. The contribution of this work will focus on thermal-hydraulic experiments to improve the understanding of the fluid flow within and around twisted elliptical tubes for use in high Prandtl number systems. This work includes scaling efforts, advanced instrumentation testing, thermal-hydraulic experiments, and flow velocimetry measurements. The scaling efforts performed are used to identify surrogate fluids for the design of future test facilities for thermal performance experiments to include twisted elliptical tubes. Advanced instrumentation testing is used to provide a proof of concept for distributed fiber systems that can be used for 2-D inflow temperature measurements. The thermal hydraulic testing will include pressure drop and initial single-side heat transfer measurements to improve the understanding and characterization of the thermal performance of twisted elliptical tubes. Velocimetry measurements were conducted using Positron Emission Particle Tracking (PEPT) to obtain velocity field measurements. The velocity field measurements are used to determine the underlying flow physics that lead the increased heat transfer. These investigations showed the tubes develop key flow features that increase mixing which in turn leads to the improved heat transfer.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
12-11-2024
Included in
Aerodynamics and Fluid Mechanics Commons, Energy Systems Commons, Heat Transfer, Combustion Commons, Nuclear Engineering Commons