Thermal Conductivity

 

Thermal conductivity refers to the core property of any and all types of material that relate to their capability to conduct heat. This means that the heat transfer in this case happens when material that are not in any form of motion are put together. This transfer of heat or energy is due to the different temperatures that the two bodies placed adjacent to each other have. Energy always flows from higher to lower temperatures according to the second law of thermodynamics meaning that a material with higher temperature is more likely to transfer its energy to an adjacent material with lower temperature (Tritt, 2006, p.6). 
 

The standard (SI) unit of measuring thermal conductivity is Watts per meter kelvin (W/mk) and is measured including variables such as mass, length, time and temperature to determine the thermal conductivity of a material (Tritt, 2006, p.5). On the other hand, convection makes material such as air and other gases bad conductors of heat hence it has to be maintained to prevent unnecessary changes. Apart from that, thermal conductivity has been recorded to track electrical conductivity since heat energy is also transferred during the transfer of electric currents across materials. Thermal anisotropy affects thermal conductivity in the sense that the direction of the thermal gradient may be same as the direction of heat flow with the presence of anisotropy due to the differences in orientation and temperature of the materials in question. Finally the chemical phase of  may affect the thermal conductivity of a material in the sense that a change from solid to liquid or liquid to gas may alter the thermal conductivity of a material.
 

A material that has higher thermal conductivity is referred to as a good conductor of heat while a material that has lower thermal conductivity is referred to as a poor conductor of heat. For example copper is a good conductor of heat due to its physical properties while wood is a poor conductor of heat. Factors that may influence a material thermal conductivity include temperature, chemical phases, thermal anisotropy, electrical conductivity, magnetic fields and convection.  Temperature has a different effect when it comes to thermal conductivity especially in metals and non-metals. Metals have free electrons roaming in them meaning that its conductivity is high as compared to nonmetals that rely on lattice vibrations (Tritt, 2006, p.13).  
 

Many processes rely on the knowledge of thermal conductivity especially in the manufacturing and processing industries. This is to ensure that the correct materials are used in making product that are used by humans. For instance, materials that have high thermal conductivity are mostly used to application that heat sink such as heaters while those material that are poor thermal conductors are commonly used as heat insulators to prevent heat loss. Additionally, processes that generate a lot of heat may require the use of materials that have high thermal conductivity to ensure that heat is channeled out to prevent overheating in the machines while materials with low thermal conductivity may be used when during construction or in small furnaces to slow heat dissipation so as to increase the rate of insulation. 

 

References

Tritt, T. M. (2006). Thermal Conductivity: Theory, Properties and Applications. New York: Springer Science and Business Media.