“…The compliance curves turned out to be similar to those typical of viscous fluids with no elasticity. Besides, the viscoelastic behavior of a material can be quantified by calculating the recovery index ΔJ (Benchabane and Bekkour, 2008;Yapici et al, 2014) given in eq. (2).…”
Impact of the nanoparticle size and concentration on the rheology of ethylene glycol based nanofluids containing nanoparticles of five different metal oxides is investigated. Particle mass concentrations ranged from 5 to 20 wt %. Types of the nanoparticles and their particle size are TiO 2 (30 nm, 50 nm), MgO (20 nm, 40 nm), [35][36][37][38][39][40][41][42][43][44][45], SiO 2 (20-30 nm, 60-70 nm) and CuO (40 nm, 80 nm). A stress controlled rheometer fitted with a cone-and-plate system is employed for the rheological characterization of the nanodispersions at temperatures between -5˚C and 35˚C. The non-linear measurements reveal that nanofluids of CuO (40 nm), ZnO (10-30 nm, 35-45 nm) and MgO (20 nm, 40 nm) particles exhibit non-Newtonian shear thinning behavior at particle mass concentrations higher than 5 %. No appreciable shear thinning is observed for the dispersions of TiO 2 (30 nm, 50 nm) and SiO 2 (20-30 nm, 60-70 nm) particles. Strong dependency between relative viscosity of the suspensions and particle size and loading is observed. Temperature, on the other hand, plays a marginal role in the relative viscosity of the suspensions. The shear viscosity measurements indicated the presence of particle size and concentration dependent apparent yield stress for CuO and ZnO nanofluids. Investigated nanofluids do not exhibit any thixotropy during their rheological characterization. Finally, viscoelastic measurements suggest that nanofluids are free of gel formation.
“…The compliance curves turned out to be similar to those typical of viscous fluids with no elasticity. Besides, the viscoelastic behavior of a material can be quantified by calculating the recovery index ΔJ (Benchabane and Bekkour, 2008;Yapici et al, 2014) given in eq. (2).…”
Impact of the nanoparticle size and concentration on the rheology of ethylene glycol based nanofluids containing nanoparticles of five different metal oxides is investigated. Particle mass concentrations ranged from 5 to 20 wt %. Types of the nanoparticles and their particle size are TiO 2 (30 nm, 50 nm), MgO (20 nm, 40 nm), [35][36][37][38][39][40][41][42][43][44][45], SiO 2 (20-30 nm, 60-70 nm) and CuO (40 nm, 80 nm). A stress controlled rheometer fitted with a cone-and-plate system is employed for the rheological characterization of the nanodispersions at temperatures between -5˚C and 35˚C. The non-linear measurements reveal that nanofluids of CuO (40 nm), ZnO (10-30 nm, 35-45 nm) and MgO (20 nm, 40 nm) particles exhibit non-Newtonian shear thinning behavior at particle mass concentrations higher than 5 %. No appreciable shear thinning is observed for the dispersions of TiO 2 (30 nm, 50 nm) and SiO 2 (20-30 nm, 60-70 nm) particles. Strong dependency between relative viscosity of the suspensions and particle size and loading is observed. Temperature, on the other hand, plays a marginal role in the relative viscosity of the suspensions. The shear viscosity measurements indicated the presence of particle size and concentration dependent apparent yield stress for CuO and ZnO nanofluids. Investigated nanofluids do not exhibit any thixotropy during their rheological characterization. Finally, viscoelastic measurements suggest that nanofluids are free of gel formation.
“…In the literature, several theories have been proposed to explain the reasons for the enhancement of heat conductivity of nanofluids. Different reasons are responsible for The enhancement of thermal conductivity; the increase in surface area and heat capacity of the fluid due to the presence of nanoparticles, the suspended nanoparticles themselves have higher thermal conductivity than that of the base fluid and the solid -liquid interface facilitates the transport of energy by the interaction and collision between the dispersed nanoparticles and the base fluid as reported by authors [9][10][11][12][13][14][15][16].…”
The article introduces artificial neural network model that simulates and predicts thermal conductivity and particle size of propylene glycol - based nanofluids containing Al2O3 and TiO2 nanoparticles in a temperature rang 20 - 80oc. The experimental data indicated that the nanofluids have excellent stability over the temperature scale of interest and thermal conductivity enhancement for both nanofluid samples. The neural network system was trained on the available experimental data. The system was designed to find the optimal network that has the best training performance. The nonlinear equations which represent the relation between the inputs and output were obtained. The results of neural network model and the theoretical models of the proposed system were performed and compared with the experimental results. The neural network system appears to yield the best fit consistent with experimental data. The results of the paper demonstrate the ability of neural network model as an excellent computational tool in nanofluid field.
“…Also, in Said et al’s results [94], the TiO 2 nanofluid with 0.1 vol.% loading was Newtonian fluid at 55 °C, whereas it was non-Newtonian below this temperature for 0.3 vol.% particle loading.Fig. 12Shear rate dependency of viscosity as a function of temperature for 5 wt.% TiO 2 –PEG200 nanofluids [118]. Reproduced with permission from Springer
…”
Section: Physical Properties Of Tio2 Nanofluidsmentioning
As a new generation of working fluid, nanofluid has long been regarded as a hot research topic in the past three decades. Many review papers have provided comprehensive and systematic summaries on the development and state-of-the-art of nanofluids. As of today, it is becoming increasingly difficult to provide a comprehensive review of all kinds of nanofluids owing to the huge amounts of the related literatures. And many controversies and inconsistencies in the reported arguments have been observed in various nanofluids. Meanwhile, the systematic or comprehensive reviews on a certain kind of nanofluid are insufficient. Therefore, this review focuses on the research about one of the hottest kinds viz. TiO2 nanofluid, which has captured scientists’ great attention because of its interesting and comprehensive properties such as sensational dispersivity, chemical stability, and non-toxicity. Due to the preparation of nanofluids is the prerequisite and physical properties are critical factors for further applications, this first part of the review summarizes recent research on preparation, stability, and physical properties of TiO2 nanofluids.
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