Supercritical carbon dioxide (sCO2) can be utilized as a working or heat transfer fluid in various thermal systems with applications in large-scale power cycles; portable power production units, coolant systems and devices. However, there are no sufficient methods and equations of heat transfer coefficient correlations, and in addition insufficient research studies about the mechanisms controlling heat transfer processes for sCO2. This study is motivated by the need to understand the intricate properties of sCO2 heat transfer and fluid dynamics with an emphasis on flow direction and inclination effects. This paper presents the study on effects of gravity, buoyancy on sCO2 flow at temperatures near and away from the pseudocritical temperature. The experimental setup consists of a high temperature and pressure sCO2 heat transfer loop and flow testing facility. Recently researched sCO2 heat exchangers can have tubes oriented at different angles such as 45° or 90° to horizontal. For the optimized design of efficient and cost-effective turbomachinery components utilizing sCO2 as the heat transfer fluid, an understanding of convective heat transfer inside a tube/pipe is equally as important as external heat transfer. A study on sCO2 heat transfer at various inclinations with angles ranging from 0°(horizontal) to 90°(vertical) along with upward and downward flow directions with different inlet temperatures is conducted. Thermocouple-based temperature measurement is utilized at multiple locations within the tube test section axially and circumferentially to study the temperature distributions on the tube surface. Volumetric heat generation is utilized to heat the external wall of the tube test section, Nusselt and Richardson numbers are calculated at circumferential wall location to show the effects of buoyancy and gravity. These Non-dimensional parameters are plotted from experimental data to show the effect of the varying parameters on heat transfer and fluid dynamics properties of the flow. it can be seen that for inlet bulk temperatures near the pseudocritical temperature, buoyant force are stronger but reduce as the inlet temperature and inclination angle is increased the buoyant forces become negligible.


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Graduation Date





Kapat, Jayanta


Master of Science in Mechanical Engineering (M.S.M.E.)


College of Engineering and Computer Science


Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering; Thermo-Fluids Track


CFE0009728; DP0027836





Release Date

August 2023

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)