Energy and exergy analysis of SiO2/Ag-CuO plasmonic nanofluid on direct absorption parabolic solar collector

Experimental investigations on the application of SiO2/Ag-CuO plasmonic nanofluid on direct/volumetric absorption parabolic solar collectors is presented in this article. The process variables for the preparation of nanofluid were optimised by employing the desirability function and response surface methodology (RSM). The optimisation was performed to achieve nanofluid with maximum possible thermal conductivity and solar absorptivity. The final solar radiation absorbed fraction and relative thermal conductivity noted for the optimised nanofluid was 82.84% and 1.234, respectively. The performance of the collector was evaluated at various flow rates from 60 lph to 90 lph, using water and optimised nanofluid as the heat transfer fluid. It is noted from the results that the thermal efficiency of the collector increases with the flow rate whereas, the exergy efficiency decreases for both water and nanofluid. The highest temperature difference of 11.27 K was noted at 60lph for nanofluid which corresponds to a thermal efficiency of 57.47%. A maximum thermal efficiency of 64.05% was noted at 90 lph which corresponds to an enhancement of 48.19% in comparison with water. Exergy efficiency of the nanofluid was enhanced by 9.4% at 60 lph, in comparison with water.