Wood

Wood properties can be calculated using the functions available in the wood module.

chemics.cp_wood(x, tk)[source]

Wood heat capacity.

Heat capacity of wood based on moisture content and temperature

\[c_{p,x} = \left(c_{p0} + c_{pw} \frac{x}{100}\right) / \left(1 + \frac{x}{100}\right) + A_c\]

where \(c_{p,x}\) is heat capacity of wet wood [kJ/(kg K)], \(c_{p0}\) is heat capacity of dry wood [kJ/(kg K)], \(c_{pw}\) is heat capacity of water as 4.18 kJ/(kg K), \(x\) is moisture content [%], and \(Ac\) is an adjustment factor that accounts for the additional energy in the wood–water bond [1].

The \(c_{p0}\) term is determined from

\[c_{p0} = 0.1031 + 0.003867\,T\]

where \(T\) is temperature in Kelvin. The \(A_c\) term is calculated from

\[A_c = x (b_1 + b_2 T + b_3 x)\]

with \(b_1 = -0.06191\), \(b_2 = 2.36e\times10^{-4}\), and \(b_3 = -1.33\times10^{-4}\).

Parameters:

  • x (float) – Moisture content as percent

  • tk (float) – Temperature in Kelvin

Returns:

cp (float) – Heat capacity of wood in kJ/(kg⋅K)

Example

>>> cm.cp_wood(12, 340)
1.91...

References

chemics.k_wood(gb, so, x)[source]

Wood thermal conductivity.

Thermal conductivity of wood based on moisture content, volumetric shrinkage, and basic specific gravity

\[k = G_x (B + C x) + A\]

where \(k\) is thermal conductivity [W/(mK)] of wood, \(G_x\) is specific gravity [-] based on volume at moisture content \(x\) [%] and \(A, B, C\) are constants.

The \(G_x\) term is determined from

\[G_x = \frac{G_b}{1 - S_x / 100}\]

where \(G_b\) is basic specific gravity [-] and \(S_x\) is volumetric shrinkage [%] from green condition to moisture content \(x\).

The \(S_x\) term is calculated from

\[S_x = S_o \left(1 - \frac{x}{MC_{fs}} \right)\]

where \(S_o\) is volumetric shrinkage [%] from Table 4-3 [2] and \(MC_{fs}\) is the fiber saturation point assumed to be 30% moisture content.

Parameters:

  • gb (float) – Basic specific gravity

  • so (float) – Volumetric shrinkage in percentage

  • x (float) – Moisture content in percentage

Returns:

k (float) – Thermal conductivity in W/(m⋅K)

Example

>>> cm.k_wood(0.54, 12.3, 10)
0.1567...

References