A pool fire is a type of

diffusion flame In combustion, a diffusion flame is a flame in which the oxidizer and fuel are separated before burning. Contrary to its name, a diffusion flame involves both diffusion and convection processes. The name diffusion flame was first suggested by ...

where a layer of volatile liquid fuel is evaporating and burning. The fuel layer can be either on a horizontal solid substrate or floating on a higher-density liquid, usually water. Pool fires are an important scenario in fire process safety and combustion science, as large amounts of liquid fuels are stored and transported by different industries.

Physical properties

The most important physical parameter describing a pool fire is the heat release rate, which determines the minimum safe distance needed to avoid burns from

thermal radiation Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...

. The heat release rate is limited by the rate of evaporation of the fuel, as the combustion reaction takes place in the gas phase. The evaporation rate, in turn, is determined by other physical parameters, such as the depth, surface area and shape of the pool, as well as the fuel boiling point,

heat of vaporization In thermodynamics, the enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to Phase transition, transform a qua ...

heat of combustion The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The ''calorific value'' is the total energy relea ...

thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

and others. A feedback loop exists between the heat release rate and evaporation rate, as a significant part of the energy released in the combustion reaction will be transmitted from the gas phase to the liquid fuel, and can supply the needed heat of vaporization. In the case of large pool fires, most of the heat transfer happens in the form of thermal radiation. Typical fuels in accidental pool fires, or experiments simulating them, include aliphatic hydrocarbons ( n-heptane, liquefied

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

gas), aromatic hydrocarbons (

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are su ...

), alcohols (

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

) or mixtures thereof (

kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...

). It is important that a pool fire involving a water-insoluble fuel is not attempted to be extinguished with water, as this can trigger explosive boiling and spattering of the burning material. Open-top tank fires are pool fires of industrial scale that occur when the roof of an atmospheric tank fails due to internal tank blast, followed by the contents of the tank catching fire. If a layer of water is present underneath the fuel and the fuel is a mixture of chemical species with several different boiling points, a

boilover A boilover (or boil-over) is an extremely hazardous phenomenon in which a layer of water under a pool fire (e.g., an open-top Storage tank, tank fire) starts boiling, which results in a significant increase in fire intensity accompanied by violen ...

may eventually occur, greatly aggravating the fire. The boilover onset occurs as soon as a hot zone propagates down through the fuel, reaching the water and making it boil.

References

{{reflist Types of fire Process safety

Physical properties

See also

References