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The law of heat conduction, also known as Fourier's law (compare Fourier's heat equation), states that the rate of heat transfer through a material is proportional to the negative gradient in the temperature and to the area, at right angles to that gradient, through which the heat flows.
For heat flow, the heat equation follows from the physical laws of conduction of heat and conservation of energy (Cannon 1984). By Fourier's law for an isotropic medium, the rate of flow of heat energy per unit area through a surface is proportional to the negative temperature gradient across it:
It quantifies how effectively a material can resist the transfer of heat through conduction, convection, and radiation. It has the units square metre kelvins per watt (m 2 ⋅K/W) in SI units or square foot degree Fahrenheit–hours per British thermal unit (ft 2 ⋅°F⋅h/Btu) in imperial units. The higher the thermal insulance, the better a ...
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, ... Transient conduction (see Heat equation) occurs when the ...
Thermal contact resistance is significant and may dominate for good heat conductors such as metals but can be neglected for poor heat conductors such as insulators. [2] Thermal contact conductance is an important factor in a variety of applications, largely because many physical systems contain a mechanical combination of two materials.
The thermal conductivity of a material is a measure of its ability to conduct heat.It is commonly denoted by , , or and is measured in W·m −1 ·K −1.. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity.
The equation of heat flow is given by Fourier's law of heat conduction. Rate of heat flow = - (heat transfer coefficient) * (area of the body) * (variation of the temperature) / (length of the material) The formula for the rate of heat flow is: = where is the net heat (energy) transfer,
The overall heat transfer coefficient is a measure of the overall ability of a series of conductive and convective barriers to transfer heat. It is commonly applied to the calculation of heat transfer in heat exchangers , but can be applied equally well to other problems.