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Heat can be considered a widely utilised and important form of energy. It is quite easily available and also plays a quintessential role in fields of scientific research. The movement of heat from surfaces of different temperatures is an important aspect associated with heat energy. It helps in the manufacturing of various heating products and also plays a crucial role in astrophysics.
The transmission of heat is done by three different means: conduction, convection, and radiation. Of this understanding, the definition of thermal conduction is very important as it takes place very frequently in nature. Thermal conduction is an extremely crucial factor in scientific research, and also in material manufacturing, it governs how well heat is transmitted through a substance.
Definition of thermal conduction:
According to the basic definition of thermal conduction, it is the process by which heat is transferred from a substance with a higher temperature to a lower temperature. This mostly happens at the molecular level.
What happens in thermal conduction?
As mentioned above, thermal conduction takes place at the molecular level. So, when a surface heats up, the molecules there start moving quickly by absorbing the heat.
These molecules, when they come in contact with molecules of other substances/surfaces with lower temperatures, pass on this energy to them.
This process continues to happen as long as heat energy is being added to the molecules.
A classic example of thermal conduction is when you put your hands on a warm window pane. This, in return, warms up your hand as well.
The molecules on the surface of the windowpane are in an excited state due to absorbing heat energy; when these molecules come in contact with the molecules on the surface of your hand, the heat is transferred to them. This warms up the surface of your hand as well.
Factors influencing thermal conduction:
The entire process of thermal conduction depends on certain factors:
The temperature gradient.
The temperature gradient is considered a physical factor that helps in governing the direction and the rate at which the temperature changes in a particular direction. Heat always flows from higher temperature to lower temperature. This transfer of temperature takes place until the temperature difference diminishes and a state of equilibrium is achieved.
The cross-sectional area of the materials/substances involved.
This is another important factor as it influences the process of thermal conduction to a great extent. The bigger the cross-sectional area of the material, the larger quantity of heat is needed to raise the temperature of the surface. Also, the bigger the surface area, the more possibilities of heat loss as well.
Physical properties of the material.
The physical properties of the substance also play a huge role in thermal conduction happening. Thermal conductivity will not happen equally for every element. Metals and stones are excellent conductors of heat, whereas materials like wood, paper, cloth are extremely poor conductors of heat.
Various aspects are associated with the conductive properties of materials.
- Conductive aspects of materials are dependent on a coefficient that is measured in comparison to silver. Silver possesses a coefficient of heat conduction of 100. Materials like iron, copper, water possess a coefficient of thermal conduction of 11, 92, and 0.12, respectively.
- A perfect vacuum is an element that is considered the most incapable in the conduction of heat. That is why its coefficient of thermal conduction is zero.
- Elements with a lower coefficient of thermal conduction are considered insulators.
- The coefficient of thermal conduction of Air is .006 and is considered an amazing insulator because we can store or trap it in an enclosed space. This is exactly why air compartments are made in artificial insulators.
- Fur, natural fibres, and feathers are exceptional insulators useful for keeping birds and animals warm. Natural fibres are again amazing in keeping humans warm during colder times. Animals like a seal, whales, walruses possess a thick layer of fat in their body which again acts as an amazing insulator. It helps in retaining the body heat when the surrounding temperature falls drastically.
- The same aspect is utilised in building spaceships as well. Small air pockets are made between the walls to retain the heat and stop the inside’s temperature from drastically reducing.
Fourier’s law of thermal conduction:
When studying the aspects and definition of thermal conduction, it is important to know about Fourier’s law of thermal conduction. According to this law, the rate at which heat energy is transferred via an element is proportional to the negative temperature gradient, and it is also proportional to the area via which the heat flows.
The differential form of the law is:
q = -k.∇T
where ∇T = temperature gradient. q = thermal flux. k = thermal conductivity of the element.
Conclusion.
To get a good idea about thermodynamics, reading about thermal conduction is extremely important. To understand the aspects of thermal conductivity, it is important to understand the definition of thermal conduction as well. Having a clear idea about insulators and elements with a higher coefficient of thermal conduction helps in understanding the working principles of multiple heating machines and insulators. In short, we can conclude that the transfer of heat from one element of higher temperature to an element of lower temperature can be described as the principle of thermal conductivity.
