Space Thermal Analysis through Reduced Finite Element Modelling

The finite element method (FEM) is widely used in mechanical engineering, in particular for structure design. However, it is not often exploited for the thermal analysis of space structures for which the use of the lumped parameter method is still commonplace. To alleviate the computational burden of the FEM for thermal analyses involving conduction and radiation, an innovative global conductive-radiative reduction scheme based on the clustering of the finite element mesh is presented. The proposed method leads to a significant reduction of the number of radiative exchange factors (REFs) to compute and size of the corresponding matrix. It further keeps accurate conduction information by introducing the concept of physically meaningful super nodes associated to the clusters from which are derived the reduced conductive couplings. To complement the reduction of the number of faces, an improved Monte Carlo ray tracing algorithm is developed. It provides better accuracy and convergence rate than the classic Monte Carlo method. The algorithm is adapted to the partitioned FE mesh and includes quadrics fitting for accurate normal representation. The resulting conductive-radiative reduced model is solved using standard iterative techniques and the detailed mesh temperatures, recovered from the super nodes temperatures, can be directly exploited for thermo-mechanical analysis. The proposed global reduction method is validated on several space structures and is benchmarked against ESATAN-TMS, the standard thermal analysis software used in the European aerospace industry