Supercritical CO2 (sCO2) has been proposed for a plethora of applications, such as power generation, air conditioning, and thermal management of electronic equipment. In proximity to critical conditions, the thermal and transport properties of the CO2 vary abruptly, promoting a significant heat transfer enhancement. Revealing the heat transfer processes associated with CO2 flows requires measuring fluid temperature, pressure, heat transfer coefficients, velocities, etc. However, fundamental knowledge about the heat transfer processes at near-critical conditions is not fully understood because of the challenges in doing such experiments at high pressures above 73 bar. Advanced optical techniques should be considered to measure these properties of sCO2. These techniques include Schlieren Imaging to capture the density gradient, LIF (Laser Induced Fluorescence) for temperature measurement, and PIV (Particle Image Velocimetry) for measurement of the velocity flow field. Different experimental setups have been built to apply the advanced optical technique. The Schlieren imaging has been applied to capture the density gradient of the methane injection into the chamber filled with CO2 at supercritical thermodynamic conditions. The density gradient in the flow helped to define the jet cone angle. The micro-channel setup was implemented through which a mixture of CO2 and Rh6G dye was flowed. The dye particles will act as a thermal probe and measure the temperature of the CO2 flow at near supercritical conditions by applying the LIF (Laser Induced Fluorescence). The PIV setup was built with a microscope to measure the velocity of the liquid CO2 flow through a T-channel. Furthermore, the bottom of the channel was painted with fluorescence color to excite, which helps to observe the shadows of the non-fluorescent particles used to measure the velocity of the flow. Current work provides the crucial knowledge needed to advance supercritical CO2 technologies for applications, including Navy ships and power plants.

Subith Vasu, Chair, MAE

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