Numerical Investigation of Thermal Exposure on External Walls in the Harmonized European Approach to Assess the Fire Performance of Façades

The European project “European Approach to Assess the Fire Performance of Facades” led by RISE, has been working toward the development of a harmonized European testing and assessment method for façade. In this study, we present numerical predictions of the thermal exposure on a noncombustible façade in the European test. Fire Dynamics Simulator (FDS), version 6.7.9, was employed as numerical model. The temperature inside the combustion chamber was underestimated by approximately 8.9%. The heat flux from the wood crib aligns well with the test results up to around 800 s, after which a deviation was observed, likely due to the way the wood crib was modeled. The heat flux at 1 m above the chamber opening was underestimated by 22.2%, while the plate thermometer temperature at the center of the fictitious window was underestimated by 17.6%. The overall trends along the vertical centerline were captured correctly, though overestimations were observed at most locations, except at 1 and 1.5 m above the chamber, with a maximum overestimation of 17.5% at 4.5 m above the chamber. The flame height was determined based on the predicted temperature, with an overestimation of 29.8%. However, this comparison has inherent limitations, primarily due to differences in the methods used to define the flame tip in experimental tests and numerical simulations. An analysis was conducted to assess the influence of the wood crib model on the fire dynamics in this large-scale test.