A homogeneous relaxation flow model for the full bore rupture of dense phase CO2 pipelines

The development of an homogeneous relaxation flow model for simulating the discharge behaviour following the full bore rupture of dense phase CO2 pipelines is presented. Delayed liquid-vapour transition during the decompression process is accounted for using an empirically derived equation for the relaxation time to thermodynamic equilibrium. The flow model's robustness is successfully demonstrated based on a series of hypothetical shock tube tests. Model validation on the other hand is performed by comparison of the predictions against experimental data obtained for the full bore rupture of realistic scale CO2 pipelines. Within the ranges investigated, it is found that although delayed phase transition effects have negligible impact on the pipeline decompression rate, ignoring such phenomena results in underestimating the transient discharge rate. This is important since the latter governs the minimum safety distances to CO2 pipelines and emergency response planning in the unlikely event of pipeline failure.