Experimental characterization on pore parameter and the irradiation absorption efficiency of a series SiC foam specimens

This paper experimentally analyzes the thermal performance of a volumetric solar receiver with a series pore structures of silicon carbide foam. Twelve silicon carbide foam specimens with various porosities and pore diameters were systematically tested on a lab-scale test platform. Three-dimensional temperature distribution, including irradiated surface temperature distribution and internal solid temperature, were obtained. Non-uniform temperature distribution on the irradiated surface and internal field, as well as the corresponding thermal efficiency under different working conditions, was analyzed. The results demonstrate that pore diameter has a more significant effect on thermal performance than porosity, as the characteristics of the specific surface area among the examined samples were mainly determined by pore diameter. For the detected solid temperatures, the highest exceeded 1000 degrees C without any damage to the porous structure, and the maximum mean outlet air temperature exceeded 544 degrees C. The thermal efficiencies of the samples with smaller pore diameter were markedly higher in most cases. The best thermal efficiency was 85.4%, which was obtained from the specimen with pore diameter of 2.27 mm and porosity of 0.663. Optimal geometric properties of SiC foam absorbers may be characterized by small pore diameter and high porosity, which can beneficial by both the advantage of uniform irradiation absorption and effective interphase convection. The experimental data presented in this paper can provide a clear reference for the theoretical model and engineering design.