Conduction is the transfer of heat through a body without displacement of the particles which make up the body. This means that all of the particles of the body or system must stay in place as heat is allowed to flow through. An example of this is boiling water in a tin can over an open flame. The tin can gets heat from the fire through radiation. However, the tin can pass the heat from the fire and transfer it to the water through conduction.
The particles in the tin are not displaced during or after the heat transfer. Fourier’s Law states that the time it takes for the heat to flow across a unit area at steady state is proportional to the temperature gradient orthogonal to the area. The thermal conductivity of the material (K) indicates the difficulty in which the heat transfers through the material. The value of K can vary from about 0.
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01 W/mK for gases to 1000 W/mK for pure metals. The thermal conductivity is dependent on a few variables such as temperature, bonding and structure of the material. The thermal conductivity for ceramic materials is lower than that of metals. Thermal conductivity is lowered when the material is porous. In addition, thermal conductivity of the material varies with the temperature.
The variation of thermal conductivity with temperature can be described by the equation below.