Numerical and experimental evaluation and optimization of ceramic foam as solar absorber - Single-layer vs multi-layer configurations

The parametric optimization studies have shown that the porosity of the foam is strongly related to the obtained thermal efficiency. The higher the porosity of the foam, the higher is also the absorber thermal efficiency. A broad plateau-like efficiency maximum can be observed for cell densities between 30 and 50 PPI (pores per inch). When applying a multi-layer configuration, no significant correlation can be observed between efficiency and the properties of the second or third layer. Only the parameters of the first layer seem to determine the thermal performance. This leads to the conclusion that an optimized single-layer configuration is the absorber of choice. If necessary, a second layer could be applied to satisfy mechanical stability aspects.