The Combined Effect of Al2O3 Nanofluid and Coiled Wire Inserts in a Flat-Plate Solar Collector on Heat Transfer, Thermal Efficiency and Environmental CO2 Characteristics

The present study experimentally investigated the thermal efficiency, collector area, weight, embodied energy, environmental CO2 emissions of Al2O3/water nanofluid flow in a flat-plate solar collector and with coiled wire turbulators. The experiments were performed at ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} that is equal to 0.1%, 0.2% and 0.3% and volume flow rate from 120 to 300 L/h. Results indicate that the collector thermal efficiency increased with the increase of particle volume loadings and volume flow rates. The thermal efficiency of the collector with water circulate is 53%, whereas it is enhanced to 65% at ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.3% nanofluid, and it is further enhanced to 77% for ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.3% nanofluid with 10-mm coiled wire insert in a collector tube at a volume flow rate of 300 L/h. The collector area is declined to 8.66% (ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.1%), 14% (ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.2%) and 18.66% (ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.3%) for nanofluids. The collector area is further reduced to 31.33% for ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.3% nanofluid and with a coiled wire pitch of 10 mm. The materials embodied energy is decreased to 1144.36 MJ for ϕ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document} = 0.3% nanofluid, and it is further reduced to 1022.6 MJ with the use of a wire coil pitch of 10 mm, but for water, it is 1451.4 MJ. The Nusselt number is increased to 23.22% with ϕ = 0.3% nanofluid, and it further enhanced to 53.56% at same particle loadings and coiled wire pitch of 10 mm over the water data.