Definition of Thermal Conductivity

Thermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.
The relationship between transported heat per unit of time (dQ/dt or heat flow Q) and the temperature gradient (ΔT/Δx) through Area A (the area through which the heat is flowing perpendicularly at a steady rate) is described by the thermal conductivity equation.

Thermal conductivity is thus a material-specific property used for characterizing steady heat transport. It can be calculated using the following equation:

Where a:  Thermal diffusivity
          cp: Specific heat capacity
          ρ:   Density

An overview of the thermal conductivity for various materials
is shown in figure 2.

Depending on the material the thermal conductivity can be measured by LFA, HFM or GHP.


In the manufacturing and processing of materials, the knowledge of the thermal properties is very important. Check out our posters in order to find the thermal properties of materials at a glance!

further related links:

Definition of Thermal Diffusivity

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