What Is a Thermal Conductor?

Thermal Conductivity

• According to the NDT Resource Center, thermal conductivity is the intrinsic property of a material which relates to its ability to conduct heat. When a temperature gradient exists within a material, heat is conducted throughout it by a transfer of energy, without any movement of the material as a whole. The heat is conducted, through transfer of energy between molecules, along the temperature gradient in the direction of decreasing temperature. Heat is conducted in this way due to the higher temperatures equating to greater molecular energy and therefore more molecular vibration. As these molecules vibrate, they collide and the energy is transferred from more- to less-energetic molecules. In thermal conductors this process occurs very quickly, meaning the material will heat up very quickly, but similarly, it will cool down quickly as the heat is conducted away.

Equation of Thermal Conductivity

• The thermal conductivity of a material can be summarized with the following equation, as demonstrated by the NDT Resource Center:

  λ = Q --- L / (A --- "T)

  Thermal Conductivity = heat --- distance / (area --- temperature gradient)

Exchange of Thermal Energy

• Exchange of thermal energy can also occur between thermal conductors. The thermal energy of a material is a measure of the speed of its particles, according to the University of Virginia Physics Department. When two materials at different temperatures come into contact with each other, the faster moving molecules collide with the slower moving molecules and energy is exchanged, heat is conducted. When this occurs, the faster moving molecules give up some energy, which is gained by the slower moving molecules making them speed up, as explained by the University of Virginia Physics Department. Eventually an equilibrium temperature is reached, in which the warmer material has cooled and the colder material has warmed, with the molecules in each moving at the same speed.

Good Thermal Conductors

• Most metals are good thermal conductors and for this reason objects such as radiators and frying pans are made using metals as they will heat up and cool down quickly and efficiently. The most efficient thermal conductors, however, are diamond and carbon nanotubes, according to David Darling's Encyclopedia of Science. This is because both diamond and carbon nanotubes have strong molecular bonds, organised in a very regular order, making it easy for molecular vibrations to travel quickly and efficiently through the materials.