Experimental Study of Supercritical CO₂ Critical Flow Through Short Tubes

The accidental leakage is one of the main risks in supercritical CO₂ power conversion system. Complex leakage behavior including critical flow and multiphase jet flow occurs at the leak, which need to be evaluated carefully for safety assessment before deployment of supercritical CO₂ power conversion system. A new experimental facility was built to study supercritical CO₂ leakage flow. The critical flow and jet flow behavior of supercritical CO₂ through short tubes were experimentally investigated. Six sharp-edged short tubes with length between 1.0 and 15.0 mm and diameter of 1.0mm were tested. The upstream temperature was examined ranging from 35 to 100°C. Effects of upstream pressure were tested ranging from 8.1 to 11.0 MPa. Critical mass flow rate of S-CO₂ decreases with the increase of upstream stagnation temperature and L/D, and increases with upstream stagnation pressure. An empirical correlation with geometric and thermal parameters is proposed based on a large amount of experimental data. The experimental data of critical flow and empirical correlation could be used for safety assessment and theoretical model validation.