Energy and exergy comparison of a flat-plate solar collector using water, Al₂O₃ nanofluid, and CuO nanofluid

The performance of a flat-plate solar collector was investigated by using water, Al₂O₃ nanofluid, and CuO nanofluid as the working fluids. The energy efficiency, entropy generation, exergy destruction, and exergy efficiency were analyzed and compared. The flat-plate solar collector exhibited the highest efficiency when the Al₂O₃ nanofluid was used as the working fluid (21.9% higher than the efficiency when water was used). The entropy generation was the highest for water and the lowest for 1.0 vol%-Al₂O₃ nanofluid. The exergy efficiency of the solar collector using 1.0 vol%-Al₂O₃ and 0.5 vol%-CuO nanofluid was improved by 56.9% and 49.6%, respectively, compared with that for water. The highest exergy efficiency of the solar collector was obtained with 1.0 vol%-Al₂O₃ nanofluid. Experimental results showed that the use of Al₂O₃ and CuO nanofluids in the flat-plate solar collector could improve the thermal efficiency compared to the use of water, and the maximum performance of the flat-plate solar collector was obtained when 1.0 vol%-Al₂O₃ nanofluid was used.