## Vertex connections -> Global System of equations

Two factors have to be accounted for when elements are connected to form the global system of equations:

(1) Continuity of the primary variables (here: temperature) across element bounds.

(2) Mass balance of secondary variables (here: heat conduction) for the element.

The principles of connecting elements shall be shown with the help of an example taken from figure to the right.

The following relations between local and global values for the temperature *T* can be derived from the figure: