The importance of real‐fluid behavior and nonisentropic effects in modeling decompression characteristics of pipeline fluids for application in ductile fracture propagation analysis

The importance of real-fluid behavior during the rapid decompression of dense natural gas mixtures has been investigated using existing one-dimensional models for real-fluid isentropic decompression (RID) and perfect-gas isentropic decompression (PID). The results show that the assumption of perfect-gas behavior may result in significant errors. In the case of ductile fracture propagation (DFP) analyses, the fracture-tip pressure level may be underestimated by more than 20 percent. A real-fluid nonisentropic decompression (RND) model has been developed in order to investigate the importance of nonisentropic effects in DFP problems. The results indicate that nonisentropic effects may be neglected for pipe sizes above approximately 508 mm O.D. On a etudie le phenomene de detente rapide de melanges de gaz naturels a l'aide de modeles unidimensionnels existangts pour la detente isentropique d'un fluide reel (RID) et la detente isentropique d'un gaz parfait (PID). Les resultats montrent que I'hypothese basee sur le modele du gaz parfait peut entrainer des erreurs importantes. Dans le cas des analyses de propagation de fracture ductile (DFP), le niveau de pression a l'extremite de la fracture peut etre sousestime de plus de 20 p. cent. On a developpe un modele de detente non isentropique de fluide reel (RND) dans le but d'etudier I'importance des effect non isentropiques lors de la propagation de fractures ductiles. Les resultats montrent que les effets non isentropiques peuvent etre negliges pour des tuyaux dont le diametre exterieur depasse 508 mm.