Prediction of heat release rate based on ceiling jet temperature in case of time-dependent fire

Abstract

By using Alpert's correlations for a ceiling jet in a steady fire, the heat release rate of the fire source can be predicted based on the operation of the fixed-temperature heat detector or sprinkler's heat sensitive device. However, as a fire grows with time in the early stage, the time until hot gases induced by a fire reach the sensor is different in proportion to the radial position, and this should be considered in order to predict the precise heat release rate based on the ceiling jet temperature. In this study, correlations for ceiling jet temperature and travelling time of hot gases are derived by dimensional analysis. The values of the coefficients in the derived correlations were deduced from the comparison with experiments. It is concluded that the travelling time of hot gases can be predicted by treating the upward flow along the plume axis and ceiling jet spreading radially as a continuous flow and that heat release rate could be predicted more precisely by considering this travelling time. Copyright © 2008 International Association For Fire Safety Science.