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

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 (& phi;tot). The Two-phase Mixture model and SST k-& omega; turbulence model have been used for simulations. The Reynolds number range is 5000 to 30,000. At a constant & phi;tot, the Nu increases with the volume fraction (& phi;) 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 co-efficient (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 & phi;tot. 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.