Abstract
The Porous Continuum method with local thermal non-equilibrium state and the P1 approximation is adopted to analyse the potentialities of using staggered stack wire meshes in double, gradual-porosity air absorbers in the axial direction. A parametric study with 300 cases, is performed considering meshes with different geometrical properties and layer thickness ratios in order to achieve greater efficiency than that offered by single-porosity metallic volumetric absorbers. The parametric study considers three different arrangements: gradually decreasing porosity, absorbers with two different layers of similar porosity and gradually increasing porosity within the air flow. The study identifies 10 configurations exceeding 90% thermal efficiency at usual working conditions. Finally, the three best configurations of the parametric analysis are experimentally tested at a small-scale laboratory test-bed and the numerical method is validated successfully in three-dimensional simulations to account for the heterogeneous solar flux profile.
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