STUDY OF THE ACCELERATED AGING OF A TWO-LAYER MATERIAL USED IN HIGH CONCENTRATION SOLAR RECEIVERS

摘要

Our aging study focuses on a superalloy coated with a high-temperature black paint which is commonly used in solar receivers. Considering the fact that the principal chemical and physical aging factors are catalyzed by the amount of solar energy that a material absorb and dissipate, a numerical model was implemented to study the thermal behavior of the material for different configurations of boundary conditions. Two sensitivity studies highlighted the most influencing boundary conditions to increase the thermal aging factors, as well as the material properties that are representative of the material aging and which need to be monitored during experimental aging tests. Different solar irradiation cycles are simulated to ascertain the optimal conditions to accelerate the degradation mechanisms. An aging process is currently being designed and a novel test-bed is introduced in this paper. We used a 2-m diameter parabolic solar furnace to perform cyclic solar irradiations on material samples that are cooled by air at the rear face. After accelerated aging tests, some important thermo-optical and thermophysical properties were monitored to analyze the decrease of the material's thermal performances. For this purpose, two devices were used: an impulse photothermal method to estimate the bulk thermophysical properties; and an optical fiber solar reflectometer to measure the directional solar reflectivity of the material's coated surface.