CO₂ pipeline depressurization: Comparison of models with reference data

We revisit the depressurization of a 50 km CO₂-transportation pipeline presented by Clausen et al. in 2012. We directly compare model predictions obtained using the commercial pipeline simulation tools OLGA and Symmetry, and the in-house research code CO₂ Dynamics. The depressurization of a high-pressure CO₂ pipeline is challenging to describe, due to the tight coupling of various effects, such as thermodynamics and phase transitions, choked flow through vent stacks, different flow regimes, giving different phase slip and friction, and strong heat transfer from the surroundings. The case was challenging for all models tested. In particular, the minimum pipe-wall temperature was lower than the observed one, which may lead to more conservative designs and operational procedures than necessary. We conclude that more data that enables separate validation of both the overall models and the various submodels are needed.