Study of the slippage of particle/supercritical CO2 two-phase flow

- Particle-SC-CO2 two-phase flow experiments have been performed.
- Particle slippage in SC-CO2 is similar to a liquid.
- Analytic calculations of slippage velocity and displacement have been derived.
- The density of SC-CO2 exerts a greater influence than the viscosity on the slippage.

In this paper, the slippage velocity and displacement between particles and supercritical CO2 (SC-CO2) were studied to reveal the particle-SC-CO2 two-phase flow behavior. Visualization experiments were performed to directly measure the slippage velocity and displacement. Eight groups of experiments involving various pressures (7.89-10.96 MPa), temperatures (38.6-47.5 °C), particle diameters (0.3-0.85 mm), particle densities (2630 and 3120 kg/m3) and SC-CO2 flow rates (0.920-1.284 m/s) were conducted. The measured particle slippage velocities in the flowing direction were approximately 10.3% of the SC-CO2 flow rate. The measured particle slippage displacements were all at the centimeter level, which indicated that SC-CO2 had a superior particle transporting capability that was similar to those of liquids even if it had a low viscosity that was similar to those of gases. A numerical model was built, and analytic slippage calculations were performed for SC-CO2 for additional analyses. The density of SC-CO2 was found to have a greater influence on the slippage than the viscosity. Moreover, a comparison of the slippage between SC-CO2 and water showed that the particle slippage in water was constant, while the particle slippage in SC-CO2 continually accumulated at an extremely slow rate.