Date of Award
2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Aerospace Systems Engineering
Committee Chair
Phillip Ligrani
Committee Member
Jason Cassibry
Committee Member
Haiyang Hu
Research Advisor
Phillip Ligrani
Subject(s)
Alloys--Mechanical properties, Additive manufacturing, Surface roughness, Heat--Transmission
Abstract
Presented are heat transfer and friction factor characteristics for four different millimeter-scale passages within additively manufactured HR-1 alloy test articles. To acquire this data, an experimental apparatus is utilized with either helium or carbon dioxide as the working fluid. A constant heat flux boundary condition is imposed along one surface of the flow passage within each test section. Test articles are manufactured using the laser powder directed energy deposition (LP-DED) additive manufacturing method. This approach is associated with significant surface roughness on the interior of flow passages. For Test Section 1 and Test Section 4 configurations, the interior surface texture is a result of no post-processing. For Test Section 2, the interior surface texture is a result of AFM or abrasive flow machining. The interior surface texture of Test Section 3 is a result of CMP or chemical mechanical polishing. Comparing data from as-built and post-processed models shows significantly lower values of the Nusselt number for all values of Reynolds number for Test Sections 2 and 3. While all test sections show an increase of the friction factor with Reynolds number, Test Sections 2 and 3 shows significantly lower values of the Darcy friction factor relative to values associated with Test Sections 1 and 4, when compared at the same Reynolds number. Data for as-built models show a higher heat transfer coefficient and Darcy friction factor compared to the models with processed surfaces. This means rougher surfaces are better for transferring heat, but their higher friction factors cause greater pressure drops compared to the models with processed surfaces. This trade-off requires consideration for the development of devices such as millimeter scale heat exchangers, combustion liners, combustors, and other heat transfer apparatus.
Recommended Citation
Blowers, Zachary, "Heat transfer and friction factors of millimeter-scale channels with surface roughness within AM HR-1 alloy material" (2026). Theses. 837.
https://louis.uah.edu/uah-theses/837