Thermal Behavior of Wood Slab Under a Truncated-Cone Electrical Heater: Experimental Observation

Abstract

With regard to the significance of thermal decomposition and ignition of wood, a set of experiments were carried out to investigate the influence of the key factors on its thermal performances. The in-depth temperature rise, solid conversion, ignition time, and ignition temperature of wood were examined when the wood slab was subjected to the radiation from a truncated-cone electrical heater. Thermal decomposition of different species performs similarly under high heat fluxes. The vertically distributed vessels in an along-grain sample facilitate the evolution of produced volatiles, and the formed char skeleton could be easily damaged to cause “cracking” among the conjunctions of vessels. The horizontal vessels in the across-grain sample give a thermally stable structure, while more energy should be consumed to break the wall of vessels. This gives rise to the shorter endurance of flaming combustion for the along-grain samples. The lag effect of moisture content on temperature rise and ignition time is observed, producing the increasing ratio of 3 s/% for ignition time against moisture content.

Keywords:

• Grain orientation
• Ignition
• Moisture content
• Thermal decomposition

ACKNOWLEDGMENTS

The authors greatly acknowledge the funding from the projects supported by the National Natural Science Foundation of China (Grant No. 51106030) and the National Basic Research Program of China (973 Program) (Grant No. 2012CB215306 and 2011CB201505).

Notes

^a Value of the density is determined as the average density of the 10 shaped wood slabs (100 mm × 100 mm × 15 mm).

^b This is the density of across-grain sample, whereas the value of along-grain sample is 743.5 kg/m³.