Thermophysical flow simulations of rapid expansion of supercritical solutions (RESS)

• We simulated thermophysical CO2 flows in RESS process.
• Whole axisymmetric flow field can be seamlessly calculated.
• CO2 condensation in the expansion chamber is evaluated.
• A simple particle-formation model predicts the formation of naphthalene particles.
• Nucleation of naphthalene starts nearly at the critical pressure.
• Location where CO2 flow crosses the critical pressure is sensitive to inlet pressure.

Thermophysical flows of rapid expansion of supercritical solutions (RESS) were numerically simulated from the nozzle inlet to the outlet of the expansion chamber. In these studies, supercritical carbon dioxide (SCO2) was used as the solvent, and naphthalene was used as the solute. Our approach seamlessly simulated SCO2 entering the nozzle, SCO2 crossing the critical pressure in the nozzle, CO2 gas expanding into the expansion chamber, and CO2 condensation in the chamber. The simulation is based on a preconditioning method developed by Yamamoto, together with mathematical models for thermophysical properties of substances in a program package for thermophysical properties of fluids (PROPATH). A primary issue was the extent to which changing the nozzle inlet and outlet pressures impacted the solubility of the solute. We also studied the effects of changing the nozzle throat diameter and throat length. In addition, we used a simple particle-formation model to predict nucleation, condensation, and coagulation of naphthalene particles. Our results indicate that the location at which the pressure crosses the critical pressure is sensitive to the pressure at the nozzle inlet, and nucleation of naphthalene starts near that location.

Figure optionsDownload as PowerPoint slide