Heat transfer and diffusion of particles
To test the understanding of the lesson
Question
Why is a metal a good heat conductor ?
Hint
Solution
Thermal conductivity goes hand in hand with electric conductivity.
Thus, metals, good electric conductors, are good thermal conductors thanks to their electrons that take part in the heat conduction phenomenon.
Question
Outline Fick's and Fourier's laws.
Give the dimensions of the thermal conductivity and , the coefficient of particle scattering.
Hint
Solution

Fourier's law :

Fick's law :
is in and in m^2.s{1}.
Question
Give the volumetric power dissipated in an ohmic conductor (with its conductivity) carrying a volumetric current .
Hint
Solution
The volumetric power is :
Question
Give the equation of heat diffusion, with and without source.
Give the equation of particle scattering, with and without source.
Hint
Solution

Equation of heat diffusion, with and without source :

Equation of particle scattering, with and without source :
Question
What is it worth for a laterally isolated rod, with its conductivity?
Hint
The thermal resistance is defined by :
Where is the thermal flow :
For an isolated rod :
Where is the length of the rod and its surface.
Solution
Question
Outline Newton's law. is the coefficient of convective exchange.
Hint
Solution
The thermal transfers between a nody and the external medium follow Newton's law is the density of the thermal flow (algebraically exiting through the surface of the material) is proportional to the temperature difference between the external medium and the surface of the material.
is called film coefficient of heat transfer.