Assessing the model error in flame extensions under ceilings formula with FDS

Abstract

Heskestad and Hamada developed a formula in 1992 to calculate the flame extension from a flame that impinged on a horizontal ceiling. The developed formula was based on seven experiments with a maximum heat release rate of 764 kW. Since 1992 there has been a development of the furniture used in homes, which in turn has led to a larger potential heat release rate from furniture fires. Today a sofa can have a potential heat release rate of 2500 kW. Since the formula is based on seven experiments and the increase of potential heat release rates in furniture fires, it is of interest to investigate if the formula developed by Heskestad and Hamada is accurate for fires with a heat release rate larger than 764 kW. In this report, the model error of Heskestad and Hamada’s flame extension formula is analyzed against simulations performed in FDS for heat release rates between 23.2 kW and 7000 kW. In total 20 simulated results were analyzed against calculations using Heskestad and Hamada’s flame extension formula. The results show a standard percentage model error of ±10.8 % between the simulated results and the calculated results using Heskestad and Hamada’s flame extension formula. The result including the uncertainties and limitations of the simulations show that the formula for flame extensions under ceilings developed by Heskestad and Hamada, can be used for fires an heat release rate between 23.3 kW to 7000 kW.