Thermal Hazard Evaluation for Process Buildings Using CFD Analysis Techniques

Thermal hazard evaluation for process buildings is an important component of standard site hazards evaluations and facility siting studies, especially with the release of the new API RP-752 in 2009. The new API RP-752 requires process facilities to analyze thermal hazards to onsite buildings and assess their impact on those structures and personnel working inside them. 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. Some structures are blast resistant, which allows them to be placed closer to process equipment and unit boundaries, but could be exposed to significant thermal hazards from potential fire in these units. Screening thermal models typically used in process safety 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 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 the thermal impact on the building decreases as the distance between the building and fire source increases, and buildings can provide protection to occupants depending on exposure time, building design, and insulation applied at the building walls. The approach described in this paper can be used to assess the appropriateness of designating buildings as Shelter In Place as opposed to an evacuation procedure during fires. The results clearly show that the detailed CFD analysis can be effectively used to simulate jet fires, assess their thermal impact on buildings, and help facilities comply with the requirements as in the new API RP-752.