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Nanofluids refers to the metal or metalloid nanometer powder dispersed in water, alcohol, oil, and conventional heat exchanger medium, prepared as a uniform, stable, high thermal conductivity of the new heat exchanger medium, which is nano-technology applied to the thermal engineering traditional areas of innovative research. Nanofluids has huge potential applications in the field of energy, chemical, automotive, construction, microelectronics, information, materials, physics, chemistry, heat transfer, and many other areas of research hotspot. This thesis the following aspects: as the reductant, sodium citrate, sodium borohydride, Ag-H2O nanofluids prepared by wet chemistry; using the dispersion method, the prepared Ag nanoparticles dispersed in ethylene glycol , the preparation of the Ag-EG nanofluids. Natural flake graphite as raw materials, preparation of graphene-H2O nanofluids. Using particle size analysis, zeta potential, transmission electron microscopy (TEM), scanning electron microscopy, atomic force microscope means of X-ray diffraction, UV - visible spectroscopy to study the influence of preparation conditions on the product structure, morphology, and in-depth study of the flow of nanofluids change and thermal conductivity. The results show that: 1) Ag nano-particles is the structure of the spherical, the average particle diameter of about 60nm, the increase of the concentration of silver nitrate, of Ag nanoparticles gathered into a chain-like structure. 2) graphene sheet structure, the monolayer thickness of approximately 0.344nm, slightly higher than the theoretical value of 0.335 nm, the surface there are different degrees of wrinkles. With the the graphene-H2O nanometer increase of the concentration of the fluid, the graphene sheet stacking phenomenon generated between. 3) Ag-H2O, Ag-EG nanofluids Newtonian nanofluids. Graphene-H2O nanofluids, its concentration is greater than 1mg · ml-1 Shi, the performance of a non-Newtonian nanofluids, on the contrary, the transition to the Newtonian nanofluids. 4) within the temperature range of 20 to 60 ° C, when the Ag nano-particles have a volume fraction of 0.121%, compared with H2O, Ag-H2O nanofluids thermal conductivity improved 8.9% to 78.5%; 25 ° C, Ag-EG The volume fraction of nanofluids 0.03vol% 0.12vol%, the thermal conductivity coefficient increased from 1.6% to 7.0%; 55 ° C, the same volume fraction changing conditions, its thermal conductivity increased from 5.0% to 24.6%. Nanofluids thermal conductivity of graphene-H2O decreases with increasing solids content increases with increasing temperature, 25 ° C, nanofluids thermal conductivity of graphene-H2O (0.2mg · ml-1) increased by 17.7 %. The innovation of this paper is to: 1 using a wet chemical method to prepare a high volume fraction of Ag-H2O nanofluids; dispersion method has a chain structure of Ag nanoparticles dispersed in ethylene glycol prepared Ag-EG nano fluid. Oxidation - reduction was first prepared the graphene-H2O nanofluids graphene monolayer sheet structure the monolayer height to 0.344nm.
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