Experimental Investigation on Viscosity of the Nanofluids with Different Parameters (original) (raw)

Experimental investigations of the viscosity of nanofluids at low temperatures

Applied Energy, 2012

The effects due to temperature and shearing time on viscosity for Al 2 O 3 /water and CNT/water based nanofluids at low concentration and low temperatures are experimentally investigated. The viscosity data were collected using a stress-controlled rheometer equipped with parallel plate geometry under up and down shear stress ramp. CNT and Al2O3 water based nanofluids exhibited hysteresis behaviour when the stress is gradually loaded and unloaded, depending also on shearing time. Experiments also showed that the nanofluid suspensions indicated either Newtonian or non-Newtonian behaviour, depending on shear rate. CNT water based nanofluid behaves as Newtonian fluid at high shear rate whereas Al 2 O 3 water based nanofluid is non-Newtonian within the range of low temperatures investigated.

Viscosity affected by nanoparticle aggregation in Al2O3-water nanofluids

Nanoscale Research Letters, 2011

An investigation on viscosity was conducted 2 weeks after the Al 2 O 3-water nanofluids having dispersants were prepared at the volume concentration of 1-5%. The shear stress was observed with a non-Newtonian behavior. On further ultrasonic agitation treatment, the nanofluids resumed as a Newtonian fluids. The relative viscosity increases as the volume concentrations increases. At 5% volume concentration, an increment was about 60% in the reultrasonication nanofluids in comparison with the base fluid. The microstructure analysis indicates that a higher nanoparticle aggregation had been observed in the nanofluids before re-ultrasonication.

Viscosity estimation of Al2O3, SiO2 nanofluids and their hybrid: An experimental study

Journal of Molecular Liquids, 2018

Over the last years, tremendous efforts were dedicated to develop new heat transfer fluids. So, the research on this topic was later on focused on nanofluids, ionanofluids, molten salts and new refrigerants. This article explores two mono-component and one bi-component nanofluid and, to be more specific, it deals with the viscosity study of stabilized Al 2 O 3 , SiO 2 water based nanofluids and their hybrid (Al 2 O 3 + SiO 2 nanoparticles diluted in water). Experimental research showed a non-Newtonian behavior of all tested nanofluids. Alumina nanofluids and the two studied hybrid nanofluids have shear-thinning behavior and silica nanofluid have a shear thickening behavior. More exactly, the overall relative viscosity is higher for alumina nanofluids if compared to SiO 2 nanofluid and, by replacing 0.5 % of SiO 2 with alumina, the viscosity increases if compared to results for SiO 2 nanofluid. Few correlations are proposed for a better estimation of the viscosity for Al 2 O 3 , SiO 2 water based nanofluids. Plus, the viscosity variation with temperature was experimentally studied for the case of hybrid nanofluids, underlying the decreasing of viscosity while temperature rise and the low hysteresis behavior while proposing two equations for the viscosity variation as temperature was increasing.

Latest developments on the viscosity of nanofluids

International Journal of Heat and Mass Transfer, 2012

The past decade has seen the rapid development of nanofluids science in many aspects. Number of research is conducted that is mostly focused on the thermal conductivity of these fluids. However, nanofluid viscosity also deserves the same attention as thermal conductivity. In this paper, different characteristics of viscosity of nanofluids including nanofluid preparation methods, temperature, particle size and shape, and volume fraction effects are thoroughly compiled and reviewed. Furthermore, a precise review on theoretical models/correlations of conventional models related to nanofluid viscosity is presented. The existing experimental results about the nanofluids viscosity show clearly that viscosity augmented accordingly with an increase of volume concentration and decreased with the temperature rise. However, there are some contradictory results on the effects of temperature on viscosity. Moreover, it is shown that particle size has some noteworthy effects over viscosity of nanofluids.

A new model for calculating the effective viscosity of nanofluids

Journal of Physics D: Applied Physics, 2009

In this paper a new equation for calculating the nanofluid viscosity by considering the Brownian motion of nanoparticles is introduced. The relative velocity between the base fluid and nanoparticles has been taken into account. This equation presents the nanofluid viscosity as a function of the temperature, the mean nanoparticle diameter, the nanoparticle volume fraction, the nanoparticle density and the base fluid physical properties. In developing the model a correction factor is introduced to take into account the simplification that was applied on the boundary condition. It is calculated by using very limited experimental data for nanofluids consisting of 13 nm Al 2 O 3 nanoparticles and water and 28 nm Al 2 O 3 nanoparticles and water. The predicted results are then compared with many other published experimental results for different nanofluids and very good concordance between these results is observed. Compared with the other theoretical models that are available in the literature, the presented model, in general, has a higher accuracy and precision.

Empirical and theoretical correlations on viscosity of nanofluids: A review

Renewable and Sustainable Energy Reviews, 2013

In the past decade nanotechnology has developed in many directions. Nanofluid is a mixture of nanosized particles dispersed in fluids. Nanofluids are new generation heat transfer fluids used in heat exchangers for energy conservation. Viscosity is an important property particularly concerning fluids flowing in a tube in heat exchangers. In this regard, an attempt has been made to review the available empirical and theoretical correlations for the estimation of viscosity of nanofluids. The review also extended to preparation of nanofluids, nanoparticle volume concentration, nanofluid temperature, particle size and type of base fluid on viscosity of nanofluids. The available experimental results clearly indicate that with the dispersion of nanoparticles in the base fluid viscosity increases and it further increases with the increase in particle volume concentration. Viscosity of nanofluid decreases with increase of temperature.

The viscosity of nanofluids: a review of the theoretical, empirical and numerical models.

The enhanced thermal characteristics of nanofluids have made it one of the most raplidly growing research areas in the last decade. Numerous researches have shown the merits of nanofluids in heat transfer equipment. However, one of the problems is the increase in viscosity due to the suspension of nanoparticles. This viscosity increase is not desirable in the industry, especially when it involves flow, such as in heat exchanger or microchannel applications where lowering pressure drop and pumping power are of significance. In this regard, a critical review of the theoretical, empirical, and numerical models for effective viscosity of nanofluids is presented. Furthermore, different parameters affecting the viscosity of nanofluids such as nanoparticle volume fraction, size, shape, temperature, pH, and shearing rate are reviewed. Other properties such as nanofluid stability and magnetorheological characteristics of some nanofluids are also reviewed. The important parameters influencing viscosity of nanofluids are temperature, nanoparticle volume fraction, size, shape, pH, and shearing rate. Regarding the composite of nanofluids, which can consist of different fluid bases and different nanoparticles, different accurate correlations for different nanofluids need to be developed. Finally, there is a lack of investigation into the stability of different nanofluids when the viscosity is the target point.