Numerical Modeling of Supercritical CO2 Leaks and its Subsequent Dispersion in the Ambient Air

An integrated 3D CFD based model to calculate the leak rates of supercritical CO2 from high pressure tanks and pipelines and its subsequent atmospheric dispersion is developed. The first component of the model takes into account the transition flow of supercritical CO2 under the action of large pressure changes through small flow passages such as orifices and leaks in high pressure pipe walls. It considers steep changes in transport and thermodynamic properties using appropriate equations of state for the wide range of pressures involved. The second component of the model calculates the large scale dispersion through the ambient air. This model includes consideration of the formation of dry ice due to sudden expansion and subsequent sublimation of dry ice due to entrainment of relatively hot ambient air. It also takes into account the effects of surrounding wind field using an atmospheric boundary layer model. The first model is validated by comparing the computed mass flow rates with the experimental data for transition flow through short-tube orifices and then for a high pressure tank of CO2 emptied through a small orifice. The second model is validated by comparing the temperature and volume fractions of CO2 at different points in the downstream of the jet during dispersion with the measurements in the latter experiment.