Which Method is the Best Suited to my Particular Sample?

Which Method is the Best Suited to my Particular Sample?

The presented methods for thermal conductivity and thermal diffusivity differ from one another primarily with regard to the recommended sample geometry and the achievable thermal diffusivity and thermal conductivity ranges.

An overview of suitable sample sizes is shown in table 1.

Table 1: Established sample geometries

Sample shapeRound or rectangularSquareRound or rectangular
Number of pieces per sample121
Diameter and/or edge lengths6 mm to 25.4 mm300 mm x 300 mm150 mm x 150 mm to 300 mm x 300 mm (or. 305 mm x 305 mm to 610 mm x 610 mm
Max. thickness6 mm100 mm100 mm (or. 200 mm)
Min. thickness0.01 mm,  dependent upon sample propertiesApprox. 1 mm, dependent upon sampleApprox. 5 mm

* Two models of HFM are available for different sample sizes

Due to their relatively large sample capacities, HFMs (Heat Flow Meters) and GHPs (Guarded Hot Plates) – the methods for direct determination of thermal conductivity – are those primarily used for inhomogeneous sample materials (insulation materials).

The Laser or Light Flash Apparatuses (LFAs) are configured to handle only much smaller sample sizes. Standard samples have a size of 12.7 mm and a thickness of 2 to 3 mm.

An overview of the various thermal conductivities depending on the used method can be seen in figure 1 and for temperature ranges in figure 2.