Energy and exergy assessment of evacuated tube solar collector using water, Fe3O4 nanofluid and Fe3O4/MWCNT hybrid nanofluid

Environmental pollution has been intensifying in many countries because of the consistent misuse of fossil fuels. It’s necessary to develop and utilize sources of solar energy. The main method to use solar energy is through the use of a solar collector. This paper aims to enhance and compare the thermal efficiency of solar collector by applying water, Fe3O4 nanofluid and Fe3O4/MWCNT hybrid nanofluid as the working fluids. The energy efficiency, exergy efficiency,exergy destruction and entropy generation were compared in this study. The evacuated tube solar collector shown the maximum efficiency when the Fe3O4/MWCNT hybrid nanofluid with mixing ration of 1/4 was used as the working fluid which was 26.4% higher than cases of the water. In addition, the exergy efficiency of the evacuated tube solar collector using 0.1 wt% Fe3O4/MWCNT hybrid(1:4) nanofluid and 0.1 wt% Fe3O4 nanofluid was improved by 55.2% and 42.1% comparing to the water, the maximum exergy efficiency was observed when Fe3O4/MWCNT(1:4) hybrid nanofluid was used. Water shown the highest entropy generation while Fe3O4/MWCNT hybrid nanofluid(1:4) shown the lowest. The results in this study indicated the thermal efficiency of evacuated tube solar collector was effectively enhanced by using Fe3O4/MWCNT hybrid nanofluids as working fluid comparing to the water and Fe3O4 nanofluid, the best performance of the evacuated tube solar collector was obtained when Fe3O4/MWCNT(1:4) hybrid nanofluid was used.