Douglas-fir 목재 가연물의 반응열과 탄화도가 연소 시 발생하는 열방출율에 미치는 영향에 관한 연구

Abstract

The heat release rate (HRR) of fires can be determined from the relationship between the thermal pyrolysis rate of combustibles and the effective heat of combustion. To accurately determine the thermal pyrolysis rate of combustibles, it is important to understand the heat of reaction of combustibles. However, this parameter is difficult to measure for combustibles, such as wood, that produce charring during combustion because they undergo a multi-step pyrolysis reaction. In this study, the ISO 5660-1 standard method was used to perform cone calorimetry experiments to understand how the HRR is affected by the heat of reaction heat and charring properties of combustibles. To this end, the HRR calculated using FDS computational analysis was compared to the measured value from the ISO 5660-1 cone calorimetry experiments. A dehydrated Douglas-fir, an evergreen tree of the pine family, was used as a combustible material. Compared to PMMA which are often used as interior materials for buildings, Douglas-fir wood was found to produce a lower rate of heat release and CO which help to lessen human damage in fire. Results obtained from FDS numerical analysis and ISO 5660-1 cone calorimetry experiments clearly demonstrates that the heat release rate varies depending on the thermal thickness and the presence of charring layer of the combustible material. Unlike PMMA specimen, which do not generate a charring layer during combustion, the charring layer developed for Douglas-fir specimen further increases the thermal thickness, reducing the amount of thermal decomposition and thus the heat release from fire. The total heat release rate calculated reached the maximm as the heat of reaction input in the FDS numerical analysis was approaching the mimunm during computational analysis increased from 2400 kJ/kg to 100 kJ/kg. The cone calorimetry experiment and FDS computational analysis results confirmed that increases in the heat of reaction and charring properties were directly correlated with the decrease in the HRR.