Thermal Conductivity

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.

Figure 1

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

           aThermal diffusivity
          cp: Specific heat capacity
          ρ:   Density


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

Figure 2

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


Related Methods

LFAGHP

HFM