Fire behavior is examined in typical building compartments. Only compartments having window vents and ceiling heights of typically 3 m are generally considered. Approximate mathematical formulations are used to describe the important physics related to developing and fully developed fires. A one-zone compartment gas-phase model, with some consideration to stratification effects, is used. Fuel properties are considered in the simplest, but most practical, terms. It is shown that the ratio of heat of combustion to heat of gasification is an important fuel variable. Both crib and pool-like fires are discussed. These represent the extremes of fuel burning rates affected by either internal or external combustion effects, respectively. Cribs tend to be controlled by their internal heat transfer and combustion rate. Pool fires are used in this context to represent fuels having a small radiation path length for their surface flames. Semenov diagrams are used to explain the characteristics of fires developing to flashover. It is shown that fuels with concurrent flame spread can lead to flashover at low compartment temperatures. Critical conditions exist in terms of fuel compartment properties. The effects of ventilation and thermal feedback are explained for fully developed fires. Fire plume temperature data suggest a maximum turbulent flame temperature in fully developed compartment fires of about 1500°C for stoichiometric and adiabatic conditions. Experimental results for crib and pool fires are presented to support the trends indicated by the approximate analyses.
展开▼
