Determining the Thermal Conductivity of Fragments and Powder

Loose materials like fragments or powder consist of the solid material and the pore filling (air). As the thermal conductivity of air is extremely low, the thermal conductivity of loose materials depends largely on the ratio of solid material to pore volume. For loose materials, the pore volume is not well defined but may change significantly when shaking the sample. Hence direct thermal conductivity tests are impossible.

Measuring Principle

For powder and fragments the so-called matrix thermal conductivity is determined (i.e. the thermal conductivity of a non-porous solid consisting of the solid material share). The air between the grains is replaced by a fluid with known thermal conductivity, then the thermal conductivity of the mixture is measured. The matrix thermal conductivity is calculated from the test result, the shares of solid material and fluid in the mixture and the known thermal conductivity of the fluid.

For details please refer to our application note (PDF) Testing fragments and powder.

Suitable Fluids

The method requires a fluid which does neither dissolve the solid sample material nor reacts chemically with it. The fluid's thermal conductivity must be known accurately. The method is valid if the thermal conductivity of the dry sample material is not higher than 15 times the thermal conductivity of the fluid. As the thermal conductivity of water at room temperature is approx. 0.6 W/mK, ist can be used as a fluid for testing materials up to 9 W/mK.

Sample Preparation

The sample may not contain coarse or sharp-edged parts larger than approx. 1 mm. Larger grains must be reduced in size.

Our Services

Simply send us your sample material. We prepare the samples, make the thermal conductivity tests and calculate the matrix thermal conductivity of your materials.

Users of a TK04 thermal conductivity meter can download detailed instructions for determining the matrix thermal conductivity in PDF format: Testing fragments and powder. In our customer download section we offer a free spreadsheet file for OpenOffice, LibreOffice or Microsoft Excel which guides you step by step through sample preparation, measuring and evaluation and automatically calculates the results.