Analysis of the Combustion Efficiencies and Heat Release Rates of Pool Fires in Ceiling Vented Compartments

Abstract

This study focuses on the combustion efficiencies and further the heat release rates for pool fires in ceiling vented compartments. The concept of plume equivalence ratio (PER) is introduced to express the ventilation conditions for the flames in such compartments. The transient PER is estimated using the fire plume theories because the complex bi-directional vent flow makes it impossible to measure or calculate directly. The combustion efficiencies can thus be predicted utilizing the empirical correlation proposed by Tewarson, and subsequently the heat release rates can be decided in combination with the fuel mass loss rates. Heptane pool fires in a small-scale ceiling vented compartment were experimentally investigated. The increment of the opening size had limited impacts on the fuel mass loss rates, but significantly raised the oxygen concentrations in the compartment; however, the oxygen concentrations at the bottom began to decrease earlier. The PERs inclined with the burning procedure until extinction in general indicating the ventilation conditions for the flame grew worse; the combustion efficiencies declined correspondingly. Increasing the opening size may improve the ventilation conditions for the flame in general and consequently increase the combustion efficiencies but it seemed to have little impacts on the heat release rates.