Nodal Network

Nodal network is an approximation method to analyze heat transfer in two dimensions (3D will be covered later). They are coved in section 4.4 of the textbook.

The item you want to analyze is sectioned into nodes (an interior node is shown below), from there the heat transfer rate into and out of the node is balanced.

All flows into/out of the node are drawn going into the node (negative heat transfer rates are used to show flows out of the node). From here the heat rate balance can be reduced significantly. See 5A - Class 2 - Finite Difference for an example derivation.

Table of Nodal Finite Difference Equations contains reduced equations for common 2D node conditions.