Thermal Hazard Evaluation for Process Buildings Using CFD Analysis Techniques

Thermal hazard evaluation of process buildings is becoming an important component of standard site hazard evaluations and facility siting studies, especially with the release of the new API RP-752 [1]. The new API RP-752 recommends that process facilities analyze thermal hazards to onsite buildings and assess its impact on structures and building occupants. Thermal loads on process and portable buildings produced by fires from process units and equipment can be significant, especially if the building is close to the fire source. Buildings designed to mitigate blast and toxic hazards can be placed closer to process equipment and unit boundaries, but could be exposed to thermal hazards from a potential fire in these units. Screening thermal models typically used in process safety (PS) applications cannot take into account detailed building geometries and how they affect thermal impact from fire on building occupants. The more robust Computational Fluid Dynamics (CFD) techniques were used in this study to assess thermal hazards from horizontal jet fires on a portable (target) building located downstream of the fire source. Jet fires were simulated and thermal radiation loads on the building were predicted using PHOENICS. ADINA was then used to estimate the thermal impact from these fires on the building occupants. Temperature rise inside the building due to the thermal loads at the building exterior surface were calculated. The results showed that thermal impact on the building decreases as the distance between the building and fire source increases. Furthermore, the results indicate that buildings can provide protection to occupants depending on exposure time, building design and insulation applied at the building walls. The results clearly show that a detailed CFD analysis can be effectively used to simulate jet fires, assess their thermal impact on buildings and help facilities comply with regulations and recommendations such as the new API RP-752.