Effect of geometry and upstream stagnation thermodynamic parameters on CO2 choked flow through orifices

Abstract Small breaks may occur in the early equipment cracks or seal failures. A comprehensive understanding of small breaks leakage is essential for early leakage detection technology development. This paper describes carbon dioxide (CO2) choked flow experiments through orifices under quasi-steady-state conditions with a nozzle 1.0 mm in diameter, covering upstream pressure range of 8.1–10.71 MPa and upstream temperature range of 310–369 K. Effect of orifice length-to-diameter ratio (L/D), upstream stagnation pressure, and upstream stagnation temperature on choked flow rate were investigated. As L/D increases, choked flow rate decreases. HRM simulated the trend of choked mass flow rate vs. L/D more reasonably. Thermal non-equilibrium phenomenon occurs in the test section. Thermal non-equilibrium degree inside orifice decreases with L/D increase. As stagnation pressure increases and stagnation temperature decrease, choked flowrate increases due to larger density. Experimental data of choked flow rate are useful in understanding small break leakage process, and verifying models or develop new models.