Improving the Performance of Unglazed Solar Air Heating Walls Using Mesh Packing and Nano-Enhanced Absorber Coating: An Energy-Exergy and Enviro-Economic Assessment

This study aims to upgrade the effectiveness of unglazed solar air heating walls (SWs) using mesh packing and nano-enhanced black paint. In this regard, two SW cases with 10 cm and 15 cm plenum thicknesses have been fabricated and tested simultaneously with different modifications. In other words, six different SW configurations have been designed and empirically investigated in this research. Unmodified SWs with two plenum thicknesses have been tested in the first experiment. Iron meshes have been utilized in both SWs in the second test. In the third experiment, the impact of the combined usage of mesh packing and Fe (iron) nanoparticle-enhanced black paint (absorber coating) at 2% w/w concentration on the performance has been evaluated. Experimental results exhibited that the combined usage of mesh packing and nano-doped paint in the SWs with 10 cm and 15 cm plenum thicknesses improved the average effective efficiency value by 29.54% and 31.20%, respectively, compared to the unmodified cases. Also, the average exergy efficiencies of the six tested SW configurations were attained in the range of 6.24-12.29%. Moreover, the findings of this study showed that reducing the plenum thickness and applying the combination of meshes and nano-coating improved the annual carbon dioxide savings by 44.72%.