Enhanced sensible heat storage capacity of nanofluids by improving the photothermal conversion performance with direct radiative absorption of solar energy

Abstract

The paper numerically investigates the fluid flow and radiative heat transfer behaviour of water-based mono and hybrid nanofluids in a direct absorption solar collector under solar irradiation boundary conditions. The effects of radiation on the heat and flow performance with operating parameters such as the type of nanoparticles, volume concentrations of nanoparticles, nanoparticle size and type of base fluids are investigated. The numerical results reveal that uniform temperature distribution is obtained with an incident radiation of 1029.81 W/m2 and that the collector performance increases with the addition of nanoparticles owing to their higher radiative properties. While the temperature gain for pure water is 5.58 K, it is estimated to be 48.72 K and 51.32 K with the volume concentrations of 70 ppm and 100 ppm for Al + Al2O3 and Al + Graphite nanofluids, respectively. Moreover, the thermal performance of the collector is positively affected by increasing the size of nanoparticle. For example, for Al + Al2O3 nanofluids at 10 ppm volume concentration, the temperature increase is 37.12 K and 42.02 K at 10 nm and 50 nm, respectively. Therefore, hybrid nanofluids can be considered as effective heat transfer fluids to increase the solar radiation absorbability, and subsequently, improve the efficiency and performance of the direct absorption solar collector.