An unsteady model for the simulation of the rapid depressurization of vessels containing two-phase mixtures in non-equilibrium conditions

Abstract

This paper describes the development of a simulation tool for the rapid depressurization (blowdown) of vessels containing two-pliase mixtures in non equilibrium conditions. The model adopts the cubic equations of state for fluids mixtures with non ideal behavior for booth the phases, i.e. vapor and liquid, and it is based on a split two fluids model considering internal heat and mass transfer processes, as well as heat transfer with the vessel wall and the external environment. In order to account the mass and energy exchanged between the gas and the liquid phase, in conditions away from the thermodynamic equilibrium, a partial phase equilibrium (PPE) type approach has been introduced. In this paper the validation of the proposed model with two different literature test cases is addressed and the role of the Peneloux correction for the employed equation of state is also investigated.