Fourier's law
of conduction
- Fourier gave a physical law for heat transfer by conduction hence it is called a law of conduction
Statement
"
Fourier's law of conduction state that the rate of heat conduction that
is heat transfer is proportional to the area measured normal to the area
measured normal to the direction of heat flow and to the temperature gradient
in that direction"
- For one dimensional or
unidirectional heat conduction
where
Q = rate of
heat conducted (W)
A = surface
area (m2)
k = the proportionality constant/ thermal conductivity/ coefficient of conductivity (W/mK)
dT/dx =
temperature gradients
The negative
sign used because as temperature decreases as length increases and heat flow is
a positive quantity.
For the slab, this law can be written as follows
- From the above figure of the slab
- For one dimensional conduction, the temperature gradient ( dT/dx ) can be written as
- Hence Fourier's law of conduction can be written as
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