The Effect Of PH On The Stability Of TiO₂-H₂O Nanofluids

With the development of microelectronic devices becoming smaller and smaller,heat exchange system and unit energy storage elements are required to develop in the direction of more efficient,more compact and lower energy.Compared with traditional heat exchange materials,nanofluids have higher heat transfer performance,so the research on nanofluids has attracted the attention of energy workers.Nanofluids have excellent properties and wide application prospects,but there are still some problems to be solved.These problems include how to prepare nanofluids with good stability,the factors that affect the thermophysical properties of nanofluids,the theoretical study of nanofluids at the micro scale,and so on.Only by solving these problems can nanofluids be widely used in engineering.Therefore,the purpose of this paper is to study the influence of pH on the stability and physical parameters of water-based titanium dioxide nanofluids,to explore the law of heat transfer performance enhanced by nanoparticles,to explore the mechanism of pH on the stability of nanofluids,and to provide a reference for its wide application in engineering.In this paper,the preparation method of Nanofluids and the factors affecting the stability are systematically described.TiO₂-H₂O nanofluids with pH value of 2,4,6,8,10 and 12 are prepared by"two-step method".The particles are TiO₂nanoparticles with particle size of 20nm and deionized water as the base fluid.The static experiment is carried out on the prepared nanofluids.The stability of nanofluids is analyzed by visual inspection.It is found that PH has a significant effect on the stability of water-based titanium dioxide nanofluids.Six groups of water-based titanium dioxide nanofluids with different pH values were characterized.The morphology of nanoparticles was observed by field emission transmission electron microscopy(TEM),and the zeta potential of the samples was measured.In terms of thermal properties,the viscosity and thermal conductivity of nanofluids under different working conditions were measured by viscometer and thermal conductivity meter.In order to make the viscosity and thermal conductivity show good comprehensive properties,P Comprehensive evaluation and analysis of ER and optimal Mo number.Qualitative analysis of nanofluid agglomerates,finishing the calculation model of viscosity and thermal conductivity of nanofluid,through the use of fractal agglomerate DLCA model,with the help of MATLAB software,design and run the model to simulate the relationship between the number of nanofluid agglomerates and settling time.The results show that the zeta values of tio2-h2o nanofluids are 24.10 and-40.60 at pH 2and 12,respectively.The thermal conductivity of the samples with pH 12 is 4%higher than that of the base solution at 20?,17%higher at 60?,6%higher than that of the base solution at 20?,14%higher at 60?,Two evaluation models show that pH=2,pH=12,and at a specific temperature The results showed that per value was less than 5,the optimal value of Mo model^Cm/Cl(27)4was less than 4,the performance was the most stable and the thermophysical property was the best.The nanofluids with pH values of 6 and 8 are in the buffer zone of zeta potential instability,with poor stability and poor thermophysical properties.The simulation results of DLCA model are consistent with the experimental results.