Date of Award

Spring 2023

Access Type

Thesis - Open Access

Degree Name

Master of Science in Mechanical Engineering


Mechanical Engineering

Committee Chair

Sandra K.S. Boetcher

Committee Co-Chair

Mark A. Ricklick

First Committee Member

Rafael Rodriguez

College Dean

Jim Gregory


Supercritical carbon dioxide (sCO2) is a promising heat transfer fluid for the refrigeration and power generation industries due to its unique thermal properties and low environmental impact. To understand it as an alternative to traditional working fluids, the thermophysical and heat transfer phenomena of sCO2 are often studied using simplified geometries (tubes). Focus has been placed on investigating averaged heat transfer trends under an array of flow conditions with either a constant wall heat flux, constant wall temperature, or conjugate thermal boundary condition. Less emphasis has been placed on studying local sCO2 heat transfer developments. Tubular sCO2 numerical models that implement either a constant wall heat flux or constant wall temperature boundary condition are often validated against tube-in-tube heat exchanger experiments involving a conjugate boundary conditions, despite the intrinsic differences between the thermal boundary conditions. The heat transfer coefficient is the primary metric used to compare model results to experiments, but detailed information regarding how comparisons are made is often omitted. In this work, the differences in local heat transfer trends of sCO2 in horizontally-oriented tubular geometries, under different thermal boundary conditions, were investigated numerically