An experimental study on energetic performance evaluation of a parabolic trough solar collector operating with Al2O3/water and GO/water nanofluids

The parabolic trough solar collector (PTSC) is one of the most developed and commercialized technologies in solar heating systems. The main purpose of this study is to utilize two samples of water-based nanofluids (0.2 wt %) made of graphene oxide (GO) and alumina (Al2O3) nanoparticles in a PTSC. First, the stability and thermophysical properties of the nanofluids were investigated by focusing on the morphology of their constituent nanoparticles. In one of the results, the values of thermal conductivity and dynamic viscosity in the GO nanofluid were obtained 9.1% and 23.4% higher than Al2O3 nanofluid. Next, the nanofluids were tested in the PTSC at three volume flow rates (1, 3, and 5 L/min). Compared to pure water, the best enhancement in thermal efficiency was observed at 1 L/min about 63.2% in GO nanofluid and 32.1% in Al2O3 nanofluid. Also, the best energetic performance (the ratio of useful energy provided to pumping energy required) of the system was realized at 1 L/min. The operational effectiveness of the nanofluids in the collector was decreased with increasing flow rate. This behavior was observed more severely in the GO nanofluid, as it showed lower energetic productivity than pure water at flow rate of 5 L/min. •GO and Al2O3 water-based nanofluids compared with the focus on nanoparticles shape.•GO nanofluid with the non-spherical clusters showed higher thermal conductivity.•GO nanofluid had the highest energetic performance in the collector at 1 L/min.•GO nanofluid lost its operational effectiveness in the collector at 5 L/min.•Al2O3 nanofluid with lower viscosity showed better energetic yield at 5L/min.