Fire Design: Direct Comparison Between Fire Curves. The Case Study of a Nursery

Abstract

According to fire safety engineering, the present study analyzes fire design settings for simulation of fire in a nursery and proposes to compare simulations developed with a natural fire curve and nominal fire curve. Comparative analysis was developed according to thermo-fluid dynamic parameters that are relevant to the safety of the exposed and for the representative period of the danger flow to the exposed, which are mainly children between 0 and 3 years of age, helpless under ordinary conditions and even more so in case of emergency. Defined conditions of structure and ventilation, Two fire simulations, differentiated by fire curve, have been implemented: First simulation: the parameters have been derived from the simulation of a fire, characterized by analytic function of Heat Release Rate (HRR) Second simulation: the HRR function was obtained ex post by making a simulation of natural fire in realistically furnished room by imposing a minimum effective primer. The simulated HRR curve, appropriately linearized, allows to estimate a Likely Fire Curve (LFC). The simulations have been developed for a time of about 15 min, starting from the ignition of fire whereas the flow of the danger is serious for exposed mainly in this first phase of fire. The comparison between the parameters of fire involved the Temperature-Time Curve and HRR-Time Curve of both simulations and the ISO 834 Curve, which is a consolidated benchmark in Fire Safety Engineering (FSE). The nominal curves have been introduced for the purpose of checking whether the structural strength and integrity: the adoption of these curves in the fire safety engineering was made by analogy, on the assumption that the phenomena of major intensity, that these curves represent, ensure a safe approach on the choice of the fire design. The study showed indeed that the analytical curve, adopted in order to verify the structural strength, produces fields of both temperature and toxic concentrations lower than those obtained with the full simulation of the natural fire in order to the phases of ignition and growth, that is, in the step that requires activation of self rescue and emergency management. This result shows that taking compliance criterion, implicitly included in the analytical curves of fire, does not have the safe requirement typical of a protection approach. The advantage in taking natural fire simulations is evident in order to derive a Likely Fire Curve that for the purposes of both Thermo-Fluid Dynamics (TFD) and exodus simulation constitutes, as shown in the specific case study of nursery, a thermo-chemical stress more appropriate for the study of the safety of exposed and in the case of fire more serious.