Mohammad Irani

Closed two-phase hydrocarbon storage tank with great storage capacity and long storage time is faced with the continually evaporation of liquid, which result in the increasing of vessel pressure and liquid hydrocarbon waste. In order to improve the performance of storage tank and estimate the Boil-off Gas (BOG), accurate and efficient method is in demand. A novel dynamic numerical method has been derived to model the effects of non-ideal thermodynamic behaviors, mass and energy transfer on hydrodynamics and vice versa using CFD methods in non-isothermal multiphase flow. Mass and energy transfer during condensation and vaporization were modeled by chemical potential at the liquid–vapor interface. Mass transfers were related to the diffusion at the interface and concentration gradients at the interface. A finite volume scheme is used to solve the equations of motion. Since the thermodynamic non-ideality of the system has been taken into account, the equilibrium calculations have been performed using the fugacity coefficient definition for both the liquid and gas phases. The equilibrium calculations were done using U-P flash calculation. The obtained results and their comparison against experimental data show that the proposed model can estimate boil-off rate and rollover in closed two-phase hydrocarbon storage tank (error for BOR estimation is less than 4%). Finally, the proposed approach is valid option to simulate the behavior of industrial scale closed liquified Natural Gas (LNG) storage tank.