A pipeline depressurization model for fast decompression and slow blowdown

• CFD-DECOM, a CFD based pipeline depressurization model has been developed.
• The model is computationally efficient.
• The model can handle both pipeline decompression and slow blowdown.
• The model is validated against 5 different release scenarios.
• The predictions are in good agreement with the measurements in all the cases.

The development and validation of CFD-DECOM, a pipeline depressurization model based on the arbitrary Lagrangian–Eulerian method (ALE) and the homogeneous equilibrium assumption is presented. In CFD-DECOM, the convection terms are separately solved from the other terms in a sub-cycled explicit manner using a sub-timestep that is only a fraction of the main computational timestep. This approach significantly simplifies the solution procedure and improves the computational efficiency. The model is validated against five release scenarios including one fast decompression of a rich gas pipeline and four slow blowdown cases of a liquefied petroleum gas pipeline. The predicted pressure, temperature and fluid inventory-time traces are found to be in good agreement with the measurements in all the cases.