Conduction of heat in soil
The equation developed by Fourier (1822) is analogous to the diffusion equation as well as the Darcy’s law for the conduction of fluid in porous media. This equation is also analogous to Ohm’s law for conduction of electricity.
Fourier’s law state that the flux of heat in a homologous body is in the direction of and proportional to the temperature gradient.
JH = -KDT Where,
JH = thermal flux (amount of heat conducted across a cross sectional area per unit time)
K = thermal conductivity
DT = spatial gradient of temperature
D = shortened representation of the three dimensional gradient