Heat of combustion in spreading wood crib fires with application to ceiling jets |
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Affiliation: | 1. VTT Technical Research Centre of Finland Ltd., Espoo, Finland;2. Aalto University, Espoo, Finland;1. State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui, 230026, China;2. BRE Centre for Fire Safety Engineering, The School of Engineering, University of Edinburgh, UK;1. SP Technical Research Institute of Sweden, Fire Research, Sweden;2. School of Transportation Engineering, Hefei University of Technology, China;3. State Key Laboratory of Fire Science, University of Science and Technology of China, China;1. Beijing Key Laboratory of Metro Fire and Passenger Transportation Safety, China Academy of Safety Science and Technology, Beijing, 100012, China;2. School of Emergency Management and Safety Engineering, China University of Mining & Technology, Beijing, Beijing, 100083, China |
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Abstract: | Responding to a challenge raised with respect to a 1989 revision of a 1979 paper on the ceiling jet of t-squared fires, we have measured the heat of combustion in the growth phase of wood cribs made of sugar pine, the test fuel in the original work, needed to generalize the ceiling jet measurements to any combustible. The present determination of the chemical heat of combustion in the growth phase, 14.1 kJ/g, is a little higher than adopted in 1989 (12.5 kJ/g, from wood sample burning with diffusion flame) but still considerably lower than employed in 1979 (20.9 kJ/g, from oxygen bomb calorimetry). More importantly, the convective heat of combustion was measured as 11.5 kJ/g, which has been employed to update the ceiling jet equations for temperature and velocity in t-squared fires. An explanation is offered for the varying, and often higher than expected ceiling-level temperatures measured with thermocouples directly over the fire in the original experiments, suggesting that both plume lean and thermocouple insertion depth may have affected the indicated temperature. |
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