Thermal Conductivity Contract Testing

We measure thermal conductivity / thermal resistivity in the range of 0.1 to 10 W/mK with an accuracy of ± 2%. Depending on sample type and size we either use the standard needle probe according to ASTM D5334-22a / ISO 22007-1 or a modified needle probe for plane surfaces (ISRM Suggested Method DOI 10.1007/s00603-016-1070-5 for determining thermal conductivity of rocks). Thermal resistivity is calculated as the reciprocal of the measured thermal conductivity.

Needle probes are suitable for soft materials or for solid samples where pre-drilling is possible. To prepare cured materials or samples that are hardening, like dried soil, guiding tubes can be used. The tubes are inserted while the material is still soft and provide measuring positions for easy needle insertion.

The surface probe, designed for very hard or brittle materials, just requires a plane and smooth sample surface. Combined with a matching sample container it is used also to determine the matrix thermal conductivity of powders.

We have extensive experience with thermal conductivity tests of solids (like rock, plastics, glass, ceramics, construction materials, wood or foodstuffs), pastes, gels and viscous liquids. Thermal resistivity of sand and soil samples is a main focus of our services, especially their use as backfills for power cables and geothermal applications. For powders and fragments, we determine the so-called matrix thermal conductivity.

Samples can be of any shape and dimensions as long as they meet the minimum size requirements. In smaller samples the heat wave produced during the measurement may be reflected by the sample boundaries and could disturb the test. Needle probe (Standard VLQ) tests using the given minimum sample sizes comply with ASTM D5334.