Modeling Fire Spread in Large Compartments Using Transient Flux-Time Product for Ignition

This paper presents the formulation of a novel fire spread model to allow the study of traveling fires in large open spaces. The fuel load for an office building, for example, is made up of clusters of workstations that are arranged in a realistic pattern on the floor plan. The fire begins with the assumed ignition of a single workstation. The fire dynamics are modeled using computational fluid dynamics (CFD) software, which allows the user to specify exact compartment parameters, such as the compartment size, wall lining, ventilation conditions, and fuel load distribution. To reduce computational expense, each object (e.g., workstation) is represented by a burner that has a heat release rate equivalent to a complete workstation, as determined by experimental tests. The fire is allowed to spread realistically from object to object through the use of an improved flux-time product ignition model. The improved flux-time product ignition model is derived to predict ignition under time-varying heat flux exposure and only requires well-documented material properties for implementation. The study validates the equivalent burner assumption and the flux-time product fire spread model for large compartments using experimental data from NIST (Hamins A (2005) Experiments and modeling of multiple workstations burning in a compartment. Nist Ncstar.). The proposed fire spread model for large compartments aims to provide more realistic fire behaviors for fire resistant design of structures while balancing accuracy with computational efficiency.