Can we hold hot objects with bare hands?? Answer will be a big No!!! So, why we can’t hold hot objects with bare hands? Answer to this question is “When we hold any hot object, Heat from that object is transferred to our body due to Conductive heat Transfer“. In this article we will discuss in detail about conduction Heat Transfer.
What is Conductive Heat Transfer?
Heat transfer within thermally conductive body or between thermally contacted bodies due to temperature difference is known as Conductive Heat Transfer.
Conduction heat transfer in solid bodies occurs due to molecular excitement or lattice vibrations due to free electrons. Whereas in liquids and gases it occurs due to molecular movements and molecular collision respectively.
Fourier’s Law (Conduction Heat Transfer Calculation)
According to Fourier’s Law:
Rate of conduction heat transfer is directly proportional to the contact area, material thermal conductivity, temperature difference and inversely proportional to the thickness.
Conductive Heat transfer (Qc) = – K A (dT / L)
Qc = Conductive heat transfer per unit time in watt
A = cross section area in square meter
k = Material Thermal Conductivity (W/mK)
dT = Temperature Differential
L = Thickness/Length of the part in Meter
(dT / L) is known as temperature gradient. It’s value is negative. Because the temperature gradient vector is in opposite direction of heat flow. Conduction heat transfer is more significant in solid bodies and it follows the first law of thermodynamics.
Thermal Conductivity For a Material
Rate of conduction heat transfer is directly proportional to material thermal conductivity. For example, Considering all other parameters equal. The rate of heat transfer will be higher in copper compared to plastic material. Because copper has a higher thermal conductivity than Aluminum.
Thermal Insulation and Thermal Conductivity
In some application resistance from heat is required. Therefore material with low thermal conductivity are used for thermal insulation. For example in heating pan holding handle is covered with Bakelite material.
Thermal and Electrical Conductivity For a Material
It is not mandatory a good conductor of electricity will be a good conductor of heat as well. For example, Diamond is a bad conductor of electricity but good conductor for heat.
|Thermal Conductivity (These values are for Indicative Purpose Only)|
|Material||Thermal Conductivity (W/mK)|
Conductive Heat Transfer Calculator
To sum up, Conduction heat transfer in solid bodies occurs due to molecular excitement or lattice vibrations due to free electrons. This is a very common type of heat transfer generally occurs in solid bodies.
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