Development of a window cooling for high temperature solar receivers

Abstract

ANSYS/FLOTRAN had been used to calcualte the air flow in a gap between two quartz glass windows. This was done to design a cooling system for high temperature solar receivers, which are used to convert concentrated sunlight into high temperature heat. The most important thermal influences as radiation exchange between the windows and the absorber as well as the radiation to space of the pressure window had been considered. With a 2D axially symmetric parametric modell the CPU time was small enough to calculate severall varitations. The aim was to find out the best geometry for the cooling window for reaching the lowest possible glass temperatures by an minimum cooling mass flow and by adherence the possible pressure drop of the cooling system. The calculations showed that the best result could be reached by giving a swirl (around the middle axis) to the cooling flow. Therefore a special flange was designed for an uniform distribution and to give the swirl to the cooling flow. After manufactoring of the cooling window, the window was measured on a 3D measurement machine and the geometrie in the CFD modell was aligned to the real geometrie. Further calculations with the “real” gemetrie showed that the pressure drop will be less and the temperatures in the windows will be a little higher then in the design geometrie.The high temperature module was tested together with an gas turbine at the Plataforma Solar de Almeria (PSA) in south Spain. The first evaluation of the measurements showed that the cooling works well. The cooling flow works like CFD calculation predicted. Even the pressure drop was near the simulations.