OpenFOAM simulations of pressurized two phase propane tanks under heat load

The exposure of a pressurized tank to an external fire is closely related to the first phase of the Boiling Liquid Expanding Vapor Explosion (BLEVE) accidental scenario. This study investigated the internal pressurization, temperature increase and phase change of two phase propane tanks exposed to fire. CFD simulations, performed in OpenFOAM Foundation software version 11, were validated against four experimental cases. Conjugate heat transfer was considered to model the heat transport from the fire through the tank wall and into the tank content. The governing equations were formulated using the Volume Of Fluid (VoF) approach, and the evaporation and condensation phenomena were approximated by the Lee model. To reduce discretization errors, a mesh sensitivity analysis and the grid convergence index (GCI) method were applied. The simulations were able to capture effectively the pressure and temperature evolution. Overall, the Mean Average Percentage Error (MAPE) of the pressure was lower than 5% in three cases, with one case reaching 8%. For temperature, the MAPE measured at three positions inside the tank was under 6% in three cases, whereas in the remaining case one position showed a value of 17%. Thermal stratification was more evident in the vapor than in the liquid domain. In the liquid domain, stratification was quantified using a dimensionless parameter and the results show agreement with literature, validating the observed thermal behavior. The validated simulations contribute to the use of open-source computational tools in the process safety research field and can be used as a basis for predictive models related to the prevention and mitigation of BLEVE accidents. • OpenFOAM CFD simulations of pressurized two phase propane tanks exposed to fire. • Solid and fluid domains coupled for temperature to enable conjugate heat transfer. • Lee phase change model for continuity and energy source terms implemented in OpenFOAM 11. • Validation against four experimental cases with varying diameter and filling degree. • Analysis of thermal stratification.