Numerical investigation of the effect of two-phase hybrid nanofluids on thermal-hydraulic performance and PEC of parabolic solar collectors

Abstract

This study investigated the effect of hybrid nanofluids Al₂O₃-SiO₂/water and Al₂O₃-CuO/water on heat transfer (HT) in parabolic solar collectors. The results revealed that, in general, the Nusselt number (Nu) and pressure drop enhance with increasing total volume fraction (ϕtot). The Two-phase Mixture model and SST k-ω turbulence model have been used for simulations. The Reynolds number range is 5000 to 30,000. At a constant ϕtot, the Nu increases with the volume fraction (ϕ) enhancement of Al₂O₃ and CuO in their corresponding hybrid nanofluids, but the pressure drops for both hybrid nanofluids do not follow the same trend as the Nu with the increment of nanoparticle concentration. Their performance coefficient does not show a uniform trend compared to the percentage of nanoparticles composition in hybrid nanofluids. For example, the value of the performance coefficient (PEC) for the percentage of Al₂O₃ (0.1%) - CuO (0.4%) and Al₂O₃ (0.75%) - CuO (0.25%) is almost equal. The maximum enhancement of Nu in Al₂O₃ (0.25%) - CuO (0.75%) /water is about 47%, and this value is 33% for the other hybrid nanofluid at the same ϕtot. Also, in addition to the total volume fraction, the performance coefficient strongly depends on the percentage of nanoparticles in the hybrid nanofluid at a fixed volume fraction. Nu increases of 26% and 48% indicate the total volume fractions of 0.5% and 1%, respectively, compared to the base fluid.