ASTM International

Standard Test Method for Calculating Thermal Diffusivity of Rock and Soil
 N D4612

Annotation

This test method involves calculation of the thermal diffusivity from measured values of the mass density, thermal conductivity, and specific heat at constant pressure. It is applicable for any materials where these data can be determined. The temperature range covered by this test method is 293 to 573 K. This test method is closely linked to the overall test procedure used in obtaining the primary data on density, specific heat, and thermal conductivity. It cannot be used as a “stand alone” test method because the thermal diffusivity values calculated by this test method are dependent on the nature of the primary data base. The test method furnishes general guidelines to calculate the thermal diffusivity but cannot be considered to be all-inclusive to capture issues related to the density, specific heat, and thermal conductivity

NOTE 1—The diffusivity, as determined by this test method, is intended to be a volume average value, with the averaging volume being ? 2 ? 10?5 m3 (20 cm3). This requirement necessitates the use of specimens with volumes greater than the minimum averaging volume and precludes use of flash methods of measuring thermal diffusivity, such as the laser pulse technique.

The values stated in SI units are to be regarded as the standard. No other units of measurements are included in this standard.

This test method is intended to apply to isotropic samples; that is, samples in which the thermal transport properties do not depend on the direction of heat flow. If the thermal conductivity depends on the direction of heat flow, then the diffusivity derived by this test method must be associated with the same direction as that utilized in the conductivity measurement.

The thermal conductivity, specific heat, and mass density measurements must be made with specimens that are as near identical in composition and water content as possible.