Preparation, Properties And Application Of Sic Nanofluids

Nanofluid is a new class of transfer fluid which containing suspended metallicand nonmetallic nanoparticles in traditional fluid. The preparation of high stablenanofluids and the research of their thermal conductivities, rheological behaviors andphoto-thermal properties are critical to the solar utilization of nanofluids; In addition,the development and research of converter valve are highly improved, But itsapplications in ultra high voltage direct current (UHVDC) transmission are hinderedby its cooling. Nanofluids could solve this problem. However, research in this area isstill relatively less.In this work, SiC nanofluids were prepared by dispersion method. X-raydiffraction (XRD)、transmission electron microscopy (TEM) and sedimentationanalysis were used to explore the phase、morphology and stability of nanofluids.Optical properties, rheological behaviors, thermal conductivities and photo-thermalproperties of the products were also investigated. The heat convection test platform forthe water-cooling radiator of the thyristor has been designed and established. Theconvection heat transfer characteristicsheat of the samples on the IGBT radiator andthe radiator of the thyristor converter valve have been studied. The results are asfollows:1) High stable SiC nanofluids can be prepared via dispersion method. Samplescan be stable for several months without any stratification.2) SiC/water and SiC/coolant nanofluids both perform Newtonian rheologicalbehaviors. Their viscosities increase with the increase of mass fraction and decrease with the increase of temperature. The viscosities of SiC/water nanofluids aresignificantly lower than that of SiC/coolant nanofluids obvious.3) SiC/water and SiC/coolant nanofluids both exhibit higher thermalconductivities than their base fluids, respectively. Both their effective thermalconductivities and thermal conductivities increase with the increase of nanofluids massfraction. With the increase of temperature, the thermal conductivities of SiC nanofluidsincrease, while the effective thermal conductivities perform a constant.The thermalconductivity of2wt%SiC/coolant nanofluids showed a9.36%enhancement than thatof the base fluid.4) SiC powders have significant absorption in the ultraviolet and near infraredwavelength. SiC/coolant nanofluids have lower transmittance than its base fluid,indicating better solar absorption ability. And the transmittance decrease with theincrease of the concentration and thickness of SiC nanofluids.5) Both the photo-thermal properties of SiC/water and SiC/coolant nanofluidsperform better than their base fluids, respectively, and increase with the nanofluidsmass fraction. Under the irradiation of laser beam with a wavelength at1064nm and apower of0.023W, the temperature of SiC/H2O and SiC/coolan nanofluids with3.0%mass fractions increased by5.8℃and6.8℃, respectively，while base fluid has littleabsorption,only0.5℃. SiC nanofluids have good photo-thermal conversion properties,which have good prospects for solar energy utilization.6) SiC nanofluids exhibits lower thermal resistance than its base fluid for bothIGBT radiator and thyristor valves radiator. That is to say, SiC nanofluids performbetter cooling effect than its base fluid. The thermal resistance decrease with theincrease of mass fraction and flow, while increase with the increase of power. Thegraphene thermal paste GK-1shows better cooling effect than all other thermal pastesused，the thermal resistance decreases by56.7%and27.9%in comparison to that of airlayer for IGBT radiator and thyristor valves radiator, respectively.