Simulation of CO₂ behaviour in flow and depressurization

There is a safety aspect related to transport and processing of CO₂ that is not sufficiently covered by available technology and knowledge, i.e. the formation of solid CO₂. At normal conditions CO₂ can exist as both gas and solid. The solid state of CO₂ is connected to pressure drop and low temperatures and can typically be a problem in connection with depressurization and pipe flow. The scope of the project is to develop software handling these issues.

The project is using the Computational Fluid Dynamic (CFD) system Brilliant as its technology platform. Brilliant has FEM abilities (Finite Element) for stress analysis, and it is designed to fully support multi-physic applications.

When a flowing gas is exposed to pressure changes, the mass per volume will change in the way that there will be more mass per volume (change of density). This is typical for a gas and we say that gas is compressible. Opposite to gas, liquid does almost not change mas per volume even if the pressure increases substantial.

Calculation of gas flow combined with big pressure variations is a challenge because of the change in density. Most solution scheme is designed for small changes in pressure and is not suitable for compressible cases. The project is now into a phase where the fundamental theory is looked into with the aim to find a better solution scheme for compressible media that undergoes big pressure changes.
The project has been working with three major activities. That is development of a new density based pressure scheme, implementation of water to the thermodynamic package and implementation of a new interface that makes it easier to implement more components for use in the thermodynamics. Also the geometrical part of the vessels has been improved and the model for solid CO₂ is included to Brilliant.