Time-resolved fire heat release rate under a ceiling based on ceiling layer measurements

Abstract

Measurement of time-resolved fire heat release rate (HRR) is important to characterize fire growth and suppression. Under certain conditions, such as large fire tests conducted under a ceiling with sprinkler protection, quantification of a time-resolved HRR is still a challenging problem. This work attempts to develop a new methodology of estimating convective and chemical HRRs for a fire under a ceiling. The instantaneous measurements of gas temperature, velocity and species concentration in the ceiling layer are used to calculate the HRRs. To verify the proposed method, two heptane pan fire tests were conducted under a ceiling and the chemical HRR was calculated from the fuel mass loss data. The results demonstrate that the proposed method can provide a time-resolved chemical HRR that is comparable to that obtained from the fuel mass loss rate. The fraction of convective HRR to chemical HRR also agrees well with the test data obtained under a calorimeter. The application to rack-storage fires under a ceiling with sprinkler suppression shows that the proposed method can provide the fire growth in the free-burn period and consistent trends for the fire development with water application.