Modeling heat transfer and pressure build-up in LPG vessels exposed to fires

Fire exposure of pressurized tanks may lead to their catastrophic rupture due to internal pressure build-up and reduction of allowable stress of the metallic shell due to temperature increase. Hence, the assessment of the thermal behavior of pressurized equipment exposed to fires is a critical issue to prevent the escalation of accident scenarios in the process industry. The present study was aimed at comparing two modeling approaches for the assessment of the heat transfer in pressurized vessels exposed to fire. In particular, two simplified lumped models based on thermal nodes were compared with a CFD (computational fluid dynamics) model implemented on ANSYS FLUENT. The models were aimed at reproducing the initial phase of the vessel heat-up, before the opening of the pressure relief valve (PRV). The models were applied to case studies of industrial interest in order to assess the expected internal pressure build-up in different fire scenarios. The comparison among model results confirmed the importance of the use of advanced simulation tools for a more precise assessment of failure conditions of vessels engulfed in fires.