Heat Transfer Framework for Selecting the Structure of Open Volumetric Air Receivers
Abstract
During the last 10 years, the interest of several authors in the use of compressible gases (as CO2 and Air) as working fluid in concentrated solar power systems (CSP) has increased significantly. These fluids allow to increase the upper limit of the operating temperatures and achieve higher conversion efficiencies. Nevertheless, achieving temperatures higher than 700°C requires the use of volumetric absorbers, which design presents two scientific challenges. The first related to the computational modeling of the transport phenomena inside the porous media, coupling the turbulent effects, compressibility, the convective heat transfer and the extinction-propagation of the concentered radiation in the solid media. And the second, related to the design process regarding the configuration, distribution and material selection of the solid media, aiming to deal with the challenging operating conditions. In that context, the present study presents a performance analysis of an open volumetric absorber using atmospheric Air as working fluid, comparing honeycomb (HC) and ceramic foam (CF) as porous media. The results show that does not exist a better configuration for all the possible operating conditions, depending on Reynolds and Nusselt numbers for selecting absorber’s structure. Key-words: Honeycomb, Ceramic foam, Porous media, and Volumetric absorber.