Experience with Finite Element Modelling for Thermal Analysis

The paper presents experience with the use of the finite element (FE) technique for thermal analysis.

The FE program NASTRAN was used to determine conductances and to calculate temperatures and thermal distortions directly at grid points of FE models. The radiative heat exchange is considered in a different way for the thermal balance of a grid point and for the balance of a node of a finite difference (FD) model. Terms of the conduction matrix between grid points of triangular elements have a physical explanation for right-angled triangles, but have only a mathematical meaning for arbitrary triangles. A method is described which allows the calculation of conductances in complicated structures without solving the heat balance equations. Examples show that a relatively fine mesh size is required in order to calculate conductances with sufficient precision. For a practical problem with conductive and convective heat transfer the FE method was, with a very fine mesh size, more precise than an approximate solution.

The FD program TMG gives indirectly the temperatures at grid points. Models with several thousands of elements could be treated with this code.