Creation of conductance matrix between boundary elements and element CG of a triangle
The conductance matrix between boundary elements and the CG of a triangle is shown in the example. The boundary element is on the left and the conductance between CG and boundary elements on the right.
The conductance matrix between boundary elements of the triangle has three conductances, while the matrix between the CG and the boundary elements has six conductances. Despite the difference between the two matrices, they are equivalent. When a triangle has a linear temperature gradient, the temperature at its CG is equal to the average temperature of the midpoints of the side edges, which gives the following equations to compute the additional conductances between the CG and the boundary elements:
where GiCG is the conductance between boundary elements and the CG.
The root mean square value of the sum of the conductances between boundary elements and the CG is minimized by:
where G12, G13 and G23 are the conductances between boundary elements in the transformed matrix.
The star-delta transformation is used to connect the conductances between boundary elements to the conductances between the CG and boundary elements as: