Thermal Diffusivity and Conductivity of Moist Porous Media

An unsteady‐state method was used to determine thermal diffusivities and conductivities of nominally 250 µm glass beads and a silt loam soil over a range of moisture contents. The thermal diffusivity of the beads was found to increase from 0.0013 cm 2 /sec for dry beads to 0.003 cm 2 /sec at 5% volumetric moisture content, but is only weakly affected by moisture contents > 5%. The thermal diffusivity of the silt loam soil increases from 0.0022 cm 2 /sec for dry soil to 0.0042 cm 2 /sec at 30% volumetric moisture content, above which it remains essentially constant with increasing moisture content. The thermal conductivities of both porous media increase with moisture content over the entire wetness range, the thermal conductivity of the glass beads increasing from 0.53 mcal °C −1 cm −1 sec −1 to 1.97 mcal °C −1 cm −1 sec −1 , and that of the silt loam soil from 0.57 mcal °C −1 cm −1 sec −1 to 2.79 mcal °C −1 cm −1 sec −1 . Measured thermal conductivities of the glass bead media were in excellent agreement with values calculated using deVries' method.