An experimental investigation on the effect of Al2O3/distilled water nanofluid on the energy efficiency of evacuated tube solar collector

The present study was designed to experimentally investigate the effect of using Al2O3/distilled water nanofluid as the working fluid, on the thermal efficiency of all-glass passive circulation evacuated tube solar collector with internal spherical coil inside the horizontal tank. The volume fraction of nanoparticles was 0.03% and 0.06% with the nanoparticles dimension 40 nm. Triton X-100 as surfactant was used in this experimental study. The performance of the ETSC using Al2O3 nanofluid and water was compared with the flow rate inside the coil was varied from 20 to 60 l/h. The present study revealed that the maximum efficiency was found to be 57.63% for 0.06 vol% of nanofluids and mass flow rate of 60 l/h. The collector efficiency shows greater enhancement with the increasing volume fractions of Al2O3 nanoparticles and flow rate. In conclusions, results suggest that Al2O3 nanofluids can be used as the working fluids in an ETSC to absorb heat from solar radiation and to convert solar energy into thermal energy efficiently.