Affiliation(s)
1. Physics Department, University of Sciences and Technology Oran Mohamed Boudiaf, Oran BP 150, Algeria
2. Preparatory School of Sciences and Techniques Oran EPSTO, Oran BP 64, Algeria
3. Forest Fire Research Centre (CEIF/ADAI), University of Coimbra, Rua Pedro Hispano 12, 3031-601, Portugal
4. Dept. of Mechanical Engineering, University of Coimbra, Pinhal de Marrocos 3030-788, Portugal
ABSTRACT
Most Mediterranean regions face a high risk to forest fires, estimation
and anticipation of this risk modeled as a stochastic propagation process
reproduces well some fire properties. This model needs information
on the behavior of the bio-physical properties of vegetation associated to
combustion. An experimental study to analyze the structure of a leaf of Laurel
shrub at different biological stages is presented; it allows following the
structural exchanges induced on the leaf by the effect of increasing
temperature. For this purpose, both dielectric and TGA (Thermogravimetric Analysis)/DTA (Differentialthermal Analysis) was performed to a
better understanding of the pyrolysis phenomenon. The results obtained provide
information on the process of thermal degradation caused by fire. The evolution
of the leaf impedance as a function of the applied frequency characterizes the
moisture loss in plant species during pyrolysis. The dielectric response
confirms the proposition to the equivalent circuit of the leaf as a composite of
liquid and solid parts. The TGA/DTA results detected the behaviour of the solid
parts in the fire under a constant heating rate, and were able to show all the
transformation subjected by the Laurel leaf until ignition and all the gases
released during it.
KEYWORDS
Impedance spectroscopy, TGA/DTA Analysis, pyrolysis, modeling, forest fire.
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