Numerical modeling of rapid depressurization of a pressure vessel containing two-phase hydrocarbon mixture

Blowdown or rapid depressurization of pressure vessels is a well-known safety process that removes overpressure at an emergency situation. Since the thermodynamic and transport properties in a vessel change remarkably during depressurization, rigorous estimation of the properties with respect to time is essential. Particularly, the temperature drop due to the expansion would cause the wall of the vessel to become brittle, and hence, it should be evaluated in an early stage of the design process. This study developed a numerical model to simulate the phenomenon of the rapid depressurization and estimate the non-equilibrium temperature changes of the vapor, liquid and vessel wall during the depressurization process, considering combined convection, nucleate boiling and transient multilayer conduction through the vessel wall. The results of this study were compared with experiment, numerical models from literature and several commercial software and showed good agreement with experimental results.