Experimental Research On The Preparation And Thermal Physical Properties Of Water-based Nanofluids

Low thermal conductivity of heat transfer fluid has become the obstacle ofresearch new type and high efficient heat transfer of cooling technology. High heattransfer performance of fluid must be developed from the perspective of fluid.Nanofluids by adding nanoparticles to base fluid usually has higher thermalconductivity than base fluid, it has become the effective way to improve the heattransfer performance of fluid. It is necessary to know accurately the thermalphysical properties data for the convenience of engineering application. Study thetype and concentration of nanoparticles, the type and concentration of dispersant,temperature, aging time and so on different factors how to effect on the thermalphysical properties of nanofluids. The main works and conclusions are as follows:1. Preparation method of the water-based naofluids.Three kind of spherical nanoparticles (CuO, α-Fe2O3, γ-Al2O3) were selected.SWNT, SWNT-OH and SWNT-COOH were selected. Four kinds of SDBS, SDS,HTAB and GA dispersant were chose. Several different nanoparticles anddispersant quality ratio of4:1,2:1,4:3and1:1were selected. A series ofnanofluids were prepared, and using the settlement observation and UV-visiblespectrophotometry to study the stability of nanofluids. These results indicated thatthe appropriate type and amount of dispersant will be different by adding differentnanoparticles to base fluid.2. Experimental research on the thermophysical properties of water-basednanofluids.Investigate the type and concentration of nanoparticles, the type andconcentration of dispersant, temperature, aging time and so on different factor howto influence on the thermal physical properties of nanofluids. These resultsindicated that the value of thermal conductivity increase has a linearrelationshipwith the concentration of nanoparticles in0.5~2.0g·L-1range,regardless of the spherical water-based nanofluids or carbon nanotubeswater-based nanofluids. But it is smaller compared with the results of predecessors.The effect on the thermal conductivity of base fluid is different for differentnanoparticles. Due to the different types of dispersant influence on the dispersionstability of nanofluids is different, both the different types of dispersant and thedispersion stability have influence on the increase rate of the thermal conductivityof nanofluids. The thermal conductivity of CuO/DIW nanofluids after aging twomonths are maximum reduced by0.20%,0.19%and0.48%than new nanofluids.Under otherwise identical conditions, the viscosity of nanofluids increases with increasing the concentration of nanoparticles and dispersant, and decrease withincreasing the temperature. The viscosity of nanofluids is higher than base fluids’.Under otherwise identical conditions, the density of nanofluids increases withincreasing the concentration of nanoparticles and dispersant, and decrease withincreasing the temperature. The density of nanofluids is smaller than base fluids’.3. Research on the thermophysical properties model of water-based nanofluids.For the thermal conductivity model of spherical nanofluids, compared theexperimental value with the Maxwell model, Yu&Choi model, Wang model andKumar model, and to improve the Kumar model. For the thermal conductivitymodel of carbon nanotube nanofluids, a model to predict the thermal conductivityof carbon nanotube nanofluids was established by considering the differentstructural properities of carbon nanotubes. For the viscosity model of nanofluids,the experimental values are greater than viscosity model values by comparingthem. For the density prediction of nanofluids, the experimental values are greaterthan the density model values by comparing them.