Thermal conductivity the list of thermal conductivities. These should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper "(see: Copper in heat exchangers)", aluminium, and silver. On the other hand, materials with low thermal conductance, such as polystyrene foam and fire brick, are used in building construction or in furnaces in an effort to slow the flow of heat, i.e. for insulation purposes. The reciprocal of thermal conductivity is "thermal resistivity", usually expressed in kelvin-meters per watt (K⋅m⋅W). For a
Thermal conductivity and it is measured in watts per square metre of surface area for a temperature gradient of 1 K per unit thickness of 1 m". Therefore, specific thermal conductivity is calculated as: where: formula_14 = temperature difference (K, or °C) = 1 K during measurement Absolute thermal conductivity, on the other hand, has units of formula_15 or formula_16, and can be expressed as where formula_18 = absolute thermal conductivity (W/K, or W/°C). Substituting formula_18 for formula_20 into the first equation yields the equation which converts from absolute thermal conductivity to specific thermal conductivity: Solving for formula_18, we get the equation