Study On The Heat Transfer And Dispersion Stability Of TiO₂ Nanofluid By Coupling TiO₂ On ZrP

As a new type of heat transfer work fluid, nanofluid has the feature of high heat conductivity coefficient which could satisfy the demand that traditional work fluid could not satisfy. But particles in fluid would aggregate as their huge surface energy and they may sediment when aggregation into bigger size which would make nanofluid change into common fluid, so lose the ability of enhance the heat conductivity coefficient. In this paper, for research the method of enhancing stability of nanofluid, a new method is proposed that nanoparticles loaded on nanoplatelets dispersed and uniformed, and control the aggregation size. The specific work as follows:Zirconium phosphate (ZrP) is synthesized by hydrothermal method whose surface is modified by 3-(Triethoxysilyl) propyl isocyanate (IPTS), then mixed with dispersed TiO2 suspension which make them loaded on ZrP nanoplatelets. At last they are exfoliated by Tetra-n-butylammonium hydroxide (TBAOH). Scanning electron microscope, transmission electron microscopy, X-ray diffractometer, laser particle size analyzer and fourier infrared spectrometer are used to analyze the samples. The results show that ZrP synthesized by hydrothermal method has the features of high purity, well-distributed size and intact shape of exfoliated platelet. By the coupling effect of IPTS, new nanocomposite particles that TiO2 nanoparticles loaded on ZrP nanoplatelets are formed. And the morphology of nanocomposite is much depended on the mass fraction ration of TiO2 and ZrP.Choosing TiO2-ZrP (1:2) nanofluid, TiO2/ZrP mixed suspensions,2 wt% TiO2 nanofluid and lwt% ZrP colloid as samples, and measuring their rheological properties and heat conductivity coefficient by rotational rheometer and thermal constant analysers. The results show that all samples are non-Newtonian fluid except DI water, ZrP have the effects of reduce the rate of shear thinning and increase the average viscosity. TiO2 nanofluid has the best heat conductivity coefficient 0.778 W/(m·K) which increases 26.3% compared to DI water. In TiO2-ZrP (1:2) nanofluid and TiO2/ZrP mixed suspensions, ZrP has the effect of reduce the heat conductivity coefficient. However the heat conductivity coefficient of TiO2/ZrP (1:2) nanofluid still increases 13.1% compared to DI water.Choosing the same samples and measuring the stability by sedimentation observation method and particles size distribution at the beginning and the 50th day by laser particle size analyzer. Then the mechanism of improving suspensions’stability by nanoplatelets’ effect is analyzed. The sedimentation results show that in the experiment time 50 days, ZrP colloid has the best stability which hardly deposit. The stability of rest samples which contain TiO2 nanoparticles, TiO2-ZrP> TiO2/ZrP> TiO2. Particles size distribution show that average size of ZrP hardly change, TiO2 nanoparticles aggregate seriously, and though TiO2-ZrP aggregate the aggregation’s size and number decreases much. There are two main reasons for improving the stability of suspension by the effects of ZrP. One is suspensions’viscosity increases by ZrP which not load nanoparticles. The other is aggregation’s size is controlled by ZrP nanoplatelets.