Wood, specific heat capacity

The FDS5 pyrolysis model is used here to qualitatively illustrate the complexity associated with material property estimation. Each condensed-phase species (i.e., virgin wood, char, ash, etc.) must be characterized in terms of its bulk density, thermal properties (thermal conductivity and specific heat capacity, both of which are usually temperature-dependent), emissivity, and in-depth radiation absorption coefficient. Similarly, each condensed-phase reaction must be quantified through specification of its kinetic triplet (preexponential factor, activation energy, reaction order), heat of reaction, and the reactant/product species. For a simple charring material with temperature-invariant thermal properties that degrades by a single-step first order reaction, this amounts to -11 parameters that must be specified (two kinetic parameters, one heat of reaction, two thermal conductivities, two specific heat capacities, two emissivities, and two in-depth radiation absorption coefficients). 

The specific heat capacity of wood depends on its temperature and moisture content but not on its density or on the wood species [12, 16, 17], Several authors have proposed a formula to determine the specific heat capacity of wood [13, 16, 18, 19]. 

Tabic I Mean values of moisture content, density, thermal conductance, specific heat capacity, void volume, ratio surface of reaction/volume of the particles of the wood samples (Fagus sylvalica - beech, Papulus x canadensis - poplar). 

The most important thermal properties of wood to consider in design are its thermal conductivity, specific heat capacity, and coefficient of thermal expansion. 

Specific heat capacity. The specific heat capacity of wood depends on the temperature and its moisture content but is practically independent of the density or species. The specific heat capacity of dry wood expressed in J.kg -K is approximately related to thermodynamic temperature T (K) by the simple equation ... 

The specific heat capacity of wood that contains water is obviously greater than that of dry wood due to the important contribution of the elevate specific heat capacity of pure water (4186 J.kg K ). Below fiber saturation, the specific heat capacity of the wood is the sum of the heat capacity of the dry wood and that of water (c J and an additional adjustment factor that accounts for the additional energy contained in the wood-water bond ... 

The specific entropy capacity plays an important role for the heat storage capacity of a material. Therefore, it has for example consequences for the behavior of construction materials during heating such as wood in case of fire. 

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