Experimental study of particle settling in supercritical carbon dioxide

• The magnitude of the settling rate in SC-CO2 is similar to that for liquid CO2.
• A new power-law relation between the Reynolds and Archimedes numbers is defined.
• A new terminal velocity formula for various SC-CO2 conditions is proposed.

In this paper, particle settling in supercritical CO2 (SC-CO2) was studied to obtain a terminal velocity calculation for engineering applications. A visualization apparatus and high-speed camera system were used to record the settling process. Fourteen sets of experiments involving various pressures (7.37–13.50 MPa), temperatures (31.5–41.0 °C), particle diameters (0.212–0.85 mm) and particle densities (2630 and 3120 kg/m3) were conducted. The terminal velocity in SC-CO2 was found to be similar to that for liquid CO2 because of the similarity of the forces acting on the particles. A power-law relationship between the particle's Reynolds and Archimedes numbers was redefined based on a dimensional analysis. Using the power-law relationship to fit the experimental results, an explicit terminal velocity formula that considers the viscosity of SC-CO2 was obtained. This formula could describe the settling rate of particles in SC-CO2 within the Reynolds number range from 1000 to 5000.

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