Understanding the Physical Phenomena of Pipeline Decompression

Pipeline decompression is an important aspect of risk assessment during the design and operation of high-pressure gas transmission pipelines. As numerical simulation technology improves, more sophisticated multiphase decompression flow models are emerging. A complete understanding of physical phenomena occurring during rapid pipeline decompression is essential in developing an accurate, advanced and fundamentally sound multiphase flow model. Pipeline decompression is a complex process that involves many thermodynamic and hydrodynamic non-equilibrium phenomena that govern the characteristics of fluid flow in the pipe. It is affected by parameters such as pipeline geometry, heat transfer, fluid characteristics, and various interactions between them. In this paper, we describe and discuss the pipeline decompression process, critical flow phenomena, fluid phase behavior, thermodynamic and hydrodynamic non-equilibria, characteristics of fluid mechanics, heat transfer and pipeline mechanics. Hopefully, this will enhance understandings of the predictive capabilities and limitations of various types of pipeline decompression models currently used for this process.