Heat Flow in the Soil
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Volume Fraction of Water
FIGURE 8.3. Thermal conductivity of mineral and organic soils from Eq. (8.1 1).
Temperature is 20" C.
permanent wilting point, so the humidity must be nearly 1 .O. The volume
fraction of minerals is 0.49, from example 1, and the water fraction is 0.2.
The gas fraction is & = 1 - 6' - 4, = 1 - 0.2 - 0.49 = 0.31.
From Eq. (8.17), the dimensionless flow factor is
The thermal conductivity of the gas phase is (Eq. (8.18)):
Note that the contribution from latent heat transport is about twice that
for conduction through the dry air. Using Eq. (8.19) the fluid conductivity
can be computed. It is