Preparation And Physical Properties Of Heat Transfer Oil Based Nanofluids

Heat transfer oil, as the master heat-transfer medium, is more and more popular in the world, whose increase of efficiency becomes master research. Generation of nanofluids promotes efficiency of heat transfer medium. Nanoparticles are added to heat transfer oil, which can improve heat transfer property of heat transfer oil. The Al2O3 and SiO2 nanofluids based on the heat transfer oil as the object of study, the best preparation process parameters of Al2O3/oil nanofluids and SiO2/oil nanofluids were determined. Then physical properties of nanafluids based heat transfer oil were measured and analyzed. The research not only provides some experiment data for further improving the heat transfer efficiency of heat transfer oil, but also provides reference of the application of nanofluids in solar thermal power system, which is of great significance in the solar thermal power generation system in engineering application and academic theory. The main research contents are as follows:1. For solving the suspension stability of nanofluids, the L9(34) orthogonal experiment was employed to analysis, selecting four parameters including the amount of oleic acid and stearic acid, stirring time, ultrasonic vibration time, each factor selecting three levels, the optimum process parameters are:oleic acid of 30%, stearic acid of 5%, magnetic stirring time of 45 min, ultrasonic vibration time of 10 min. Al2O3 and SiO2 nanofluids based heat transfer oil with different particle sizes, volume fractions were prepared by the optimum process parameters.2. The thermal conductivity of Al2O3/oil nanofluids and SiO2/oil nanofluid were measured and analyzed, on which the effect of temperature, volume fraction and particle size were analyzed. The result shows that Al2O3/oil nanofluids thermal conductivity maximum increasing rate was 19.49%, SiO2/oil nanofluids thermal conductivity maximum increasing rate of 15.25%.3. The viscosities of oil based nanofluids were analyzed in experiment and theory, on which the effect of temperature, volume fraction and particle size were analyzed. Results show that 0.2% volume fraction of Al2O3(30nm)/oil and SiO2(30nm)/oil nanofluids are decreased by 74.96% and 76.89% from 25℃ to 65℃, Al2O3/oil and SiO2/oil nanofluids viscosity increase by 17.34% and 25.37% when the volume fraction increases from 0.1% to 1.0%, the particle size of nanofluids influence viscosity with varying degrees, but the rule is not obvious.4. The wettability of oil based nanofluids was analyzed in experiment and theory, in two aspects of the surface tension and contact angle. Results show that the contact angle of nanofluids are less than these of heat transfer oil, surface tension of nanofluids are greater than these of heat transfer oil, the wettability of nanofluids are better than these of heat transfer oil.5. The device of photo thermal experiment used in the experiment was assembled by self, by which the photo thermal of oil-based nanofluids was studied. Also, radiation heat transfer coefficients between the adiabatic box and the heat transfer oil and nanofluids were calculated and analyzed. Further, experimental results were analyzed by the light absorption properties and photo thermal conversion efficiency, showing that adding nanoparticles to heat transfer oil obviously improved the photo thermal performance and 0.2% and 0.5% volume fraction of nanofluids had better photo thermal property.