Porous foams and nanofluids for thermal performance improvement of a direct absorption solar collector: An experimental study

In this study, attention is focused to examine experimentally how utilization of porous foams, as well as nanofluids, may improve thermal performance of a residential–type direct absorption solar collector (DASC). The experiments are undertaken for SiC ceramic as the porous foam and SiC–water suspension as the nanofluid. Three levels are chosen for the reduced temperature difference, the porous foam, and the volumetric flowrate while four levels are selected for the nanoparticle concentration. To determine the relative importance of each of the involved parameters on thermal efficiency of the DASC, an ANOVA is undertaken. The best thermal performance is achieved in a case having both the metal foam and the nanoparticles. The maximum rises in thermal efficiency due to the insertion of the porous foam and the inclusion of the nanoparticles are recorded to be 14% and 37%, respectively. However, it is found that the volumetric flowrate is the dominant parameter in this system in a way that the inclusion of the porous foam or the nanoparticles deteriorates its role. Comparison of the results of the two porous foams demonstrates that the foam having higher porosity and pore density leads to higher thermal efficiency.