Visualization of nucleation of supercritical carbon dioxide flow through a nozzle
Lim, Chang Hyeon
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Interest in fundamental properties of carbon dioxide near the critical point led to an investigation of supercritical CO2 flow through a converging-diverging nozzle. To study a phase change and flow behavior of supercritical CO2 flow, a closed-loop carbon dioxide loop is built with optically accessible test section. Unlike studies in which most of the experiment were performed in a blowdown facility, a steady-state closed carbon dioxide loop is built to visually inspect a nucleation behavior near the critical point. In addition, a high-speed optical diagnostic is performed on the test section to interpret the nucleation behavior in the order of microsecond. Three different parameters (pressure, temperature, and flow rate) for the supercritical flow is controlled with a specific converging-diverging nozzle geometry. Theoretical flow calculation using homogeneous equilibrium model is computed to compared with the experiment flow properties. With the high-speed diagnostics, the specific geometry yields a dominant shedding frequency that governs the flow behavior near the critical point.