In this section we will develop the finite difference formulation of heat conduction
in a plane wall using the energy balance approach and discuss how to
solve the resulting equations. The energy balance method is based on subdividing
the medium into a sufficient number of volume elements and then
applying an energy balance on each element. This is done by first selecting
the nodal points (or nodes) at which the temperatures are to be determined and
then forming elements (or control volumes) over the nodes by drawing lines
through the midpoints between the nodes. This way, the interior nodes remain
at the middle of the elements, and the properties at the node such as the
temperature and the rate of heat generation represent the average properties of
the element. Sometimes it is convenient to think of temperature as varying
linearly between the nodes, especially when expressing heat conduction between
the elements using Fourier’s law.