Enhancement of ray tracing method for radiative heat transfer with new isocell quasi-monte carlo technique and application to eui space instrument

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.This paper presents the developments of the new isocell quasi- Monte Carlo ray tracing method for thermal analysis. The rationale for this research is the speed-up of radiative heat transfer computation with the Finite Element Method, widely used in mechanical engineering especially for space structure design but not yet often for thermal analysis of these structures. Based on Nusselt’s analogy, the ray direction sampling is done by sampling the unit disc to derive the ray directions. Stratified sampling is applied to the unit disc that is divided into cells or strata into which random points are generated. The isocell method relies on cells that have the particularity of presenting almost the same area and shape. This enhances the uniformity of the generated quasi-random sequence of ray directions and leads to faster convergence. The isocell method is associated with different surface sampling to derive REFs. The method is benchmarked against ESARAD, the standard ray tracing engine of the thermal analysis software used in the European aerospace industry. Various geometries are used. In particular, one entrance baffle of the Extreme Ultraviolet Imager (EUI) instrument developed at the Centre Spatial de Li`ege in Belgium is presented. The EUI instrument of the Solar Orbiter European Space Agency mission and will be launched in a 0.28 perihelion orbit around the Sun in 2018.