Rheological Behavior Of Nanofluids Research Articles

Effect of the concentration of carbon nanotubes (CNTs) on the rheological behavior in a lubricating oil of plant-derived lubricant

Nanofluids have attracted a lot of attention since their significant enhancement in thermal properties, however there are few reports on the study of the viscosity of nanofluids from an experimental point of view. In this work, the rheological behavior of functionalized multi-walled carbon nanotubes (F-MWCNTs) and coated with MoS2 (MWCNTs-MoS2) in a commercial palm oil as base fluid was evaluated. The purification and functionalization process of the MWCNTs was performed by acid leaching and investigated by FTIR, and stable nanofluids were prepared with MWCNTs concerning time. The rheological behavior of nanofluids with MWCNTs was performed as a function of temperature at different concentrations (0.1, 0.5 and 1% wt.). The effect of time, temperature, shear rate and shear stress versus shear rate were determined. The results indicate that the nanofluid behaves as a Newtonian fluid independently of the MWCNTs concentrations and temperatures evaluated. The viscosity index increases by 16% at a concentration of 1% wt. of F-MWCNTs and for nanofluids added with MWCNTs-MoS2 had significant effect on the effect of temperature.

Experimental Study and ANN Analysis of Rheological Behavior of Mineral Oil-Based SiO2 Nanofluids

This work reports an experimental and theoretical analysis of the rheological properties of mineral oil-based SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanofluid for their potential applications in transformer insulation. The flow electrification mechanism on the nanofluids with different surfactants such as cetyl trimethyl ammonium bromide (CTAB), oleic acid, and Span 80 is studied using a spinning disk technique. The results show a higher streaming current for the nanofluids with CTAB as a surfactant compared to oleic acid and Span 80. The rheological behavior of nanofluids is explored with the double gap concentric cylinder geometry. The variation of shear stress with shear rate follows a power law relationship along with a yield stress observed for all the nanofluids. A transition is seen from storage modulus to dominant loss modulus for the nanofluids during the frequency sweep analysis, whereas no transition is observed in the case of mineral oil. In addition, regression analysis using artificial neural network (ANN) algorithms are performed on the experimentally measured viscosity of the nanofluids in order to estimate theoretical parameters and provide insights into the streaming current formation. The desirable rheological characteristics of nanofluids are identified for achieving enhanced insulation performance in transformers.

Steady Flow of Burgers’ Nanofluids over a Permeable Stretching/Shrinking Surface with Heat Source/Sink

An engineered fluid, called nanofluid, is expected to have better thermal conductivity than conventional working fluids. The superior heat transfer performance and various possible applications promote the analysis of nanofluids in different flow geometries. This paper studies the flow of non-Newtonian Burgers’ nanofluids over a permeable stretching/shrinking surface with a heat source/sink. In the current study, we highlight the use of the single-phase nanofluid model in studying the boundary layer flow. The basic partial differential equations are transformed into ordinary (similarity) differential equations. Then, the resulting equations and boundary conditions are solved numerically in MATLAB using the bvp4c package. Triple solutions are presented, and stability analysis certifies that the first solution is physically realizable in practice. It is found that the increment of the heat source parameter raised the temperature profile of the nanofluids. Al2O3/H2O and Cu/H2O nanofluids produced the highest skin friction coefficient in the flow over stretching and shrinking surfaces, respectively. Meanwhile, Cu/H2O nanofluid showed a better heat transfer performance when compared to Al2O3/H2O and TiO2/H2O nanofluids. The present study is novel and could serve as a reference to other researchers for further analysis of heat transfer performance and the rheological behavior of nanofluids.

Impact of thermal conductivity on the thermophysical properties and rheological behavior of nanofluid and hybrid nanofluid

A mathematical model is realistic to assess a comparative study of nanofluid and hybrid nanofluid flow between two eccentric pipes. Study of nanofluid has been developed recurrently over the earlier era. By taking the nanofluid study in higher level, the researchers tried to use hybrid nanofluid, which was modeled by placing different nanoparticles either in composite or mixture form. The method of using hybrid nanofluid is to get more thermal conductivity of base fluid. For this phenomena, we consider Ni and $$\gamma Al_2O_3$$ as nanoparticles and $$C_2H_6O_2$$ as a base fluid. The inner pipe is rigged and rotating with velocity (V), whereas the external pipe is sinusoidal (wave moving down to its boundaries) like the contracting and relaxation phenomena. Low Reynolds number and long wavelength approximation are used for analytic solution. The resulting nonlinear PDEs are converted into ODEs by using perturbation technique. After this, we compare graphically the behavior of friction forces on inner and outer pipes, pressure gradient, pressure rise, velocity and temperature profiles for multi-values of solid volume fractions.

A new generation of hybrid-nanofluid: thermal properties enriched lubricant fluids with controlled viscosity amount

The experimental rheological behavior study on Multi-Wall Carbon Nanotube (MWCNT)-TiO2 (40:60)/SAE50 hybrid nanofluid (NF) is the main subject of present work. The experiment conditions are temperature range of 25–50 °C and solids volume fractions of 0–1% at a shear rate (SR) range of 666.5–9331 s−1. The results show that at an SR of 3999 S−1, the viscosity decreases by 76% when increasing the temperature at a concentration of 1%. Based on the results, NFs exhibit non-Newtonian behavior in all concentrations. Since the power-law index is less than 1 at all temperatures and volume fractions, its behavior is of pseudoplastic type. The results show that hybrid NFs at all solid volume fractions (SVFs) less than 0.5% has a viscosity lower than the base fluid. The sensitivity analysis and economic evaluation of using hybrid NFs are the other analyzed parameters in present study. The sensitivity analysis achieves its maximum value at SVF of 1% and the temperature of 50 °C, and its minimum value at SVF of 0.0625% and the temperature of 25 °C. In addition, to predict the viscosity of hybrid NFs, this study propose a three variable novel experimental model with a coefficient of determination (R2) of 0.9882. Also investigation on hybrid NF effect on rheological behavior of NFs is another question in present study that is answered compeletely.

Viscosity and rheological behavior of aqueous nanofluids containing TiO2 nanoparticles

Nanofluids containing different concentration of TiO2 nanoparticles were prepared. Their rheological behavior was investigated on LVDV III ultra-programmable Brookfield viscometer at different temperature and particles loading. Results show that rheological behavior of nanofluids is determinated by the concentration of TiO2 in base fluid, nanofluids shows good Newton behavior when nanoparticles loading is low, while shear thinning becomes evident when the volume fraction of particles was continuously increased. Besides, viscosity of nanofluids shows strong nanoparticles loading and temperature dependence, but quite differs from classical viscosity model, as the theory models severely underestimate the value of viscosity, which is attributed to electroviscous effect of nanoparticles in base fluids. The primary electroviscous coefficient is evaluated at different pH values. Modified primary electroviscous coefficient is in good agreement with Booth’s theory.

Influences of Temperature, Concentration and Shear Rate on Rheological Behavior of Nanofluid: An Experimental Study with Al2O3-MWCNT/10W40 Hybrid Nano-Lubricant

In this experimental study, the rheological behavior of Al2O3-MWCNT (90%:10%)/10W40 hybrid nano-lubricant has been determined at the temperature range of 5°C to 55°C. Al2O3 nanoparticles (average size of 50 nm) and MWCNTs (inner and outer diameter of 2-6 nm and 5-20 nm, respectively) were dispersed in engine oil (10W40) to prepare 0.05%, 0.1%, 0.25%, 0.5%, 0.75% and 1% solid volume fractions. For each sample, dynamic viscosity was measured at shear rates ranging from 666.5 s-1 to 13330 s-1 with an uncertainty of about 0.6%. The findings insinuated that at the most range of temperature and solid volume fraction the nano-lubricant, as well as the base oil, are non-Newtonian fluids. Thus, by curve fitting the indexes of power law and consistency were calculated. Eventually, the correlations indicated a very well compromise with experimental data.

Characterization and Colloidal Stability of Surface Modified Zinc Oxide Nanoparticle

This paper mainly studies the characterization and colloidal stability of surface modified zinc oxide nanoparticle and pure zinc oxide nanoparticle. According to IUPAC definition, ultrafine particles are always in the range of within 100 nm called nano-sized particle which expressed in term of perfect spherical diameter. Nanotechnology has immersed into various sector of oil and gas industries. In recent decades, vast amount of research has been done using zinc oxide nanoparticle related products effect on disjoining pressure mechanism in porous medium, interfacial tension (IFT) and wettability. Several types of nanoparticles have been evaluated through interfacial tension and wettability. Disadvantage of poor colloidal stability of nanoparticle in fluid is aggregation and sedimentation which leads poor heat transfer. In this study, zinc oxide nanoparticle was used as core to be functionalized. Surfactant was used to surface modify ZnO nanoparticle. Surface modified ZnO nanoparticle and pure ZnO nanoparticle were characterized using Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Stability and hydrodynamic size of surface modified and pure zinc oxide nanofluid are examined using Zetasizer Nano ZS. Rheological behavior of nanofluids were determined through rheometer. The peak of surface modified and pure ZnO nanofluid were 62.94 nm and 386.4 nm respectively. There is a decrease of 83.71% of hydrodynamic size of nanoparticle after surface modified. ZnO nanofluid has the stability of -14.2 mV while surface modified ZnO has the zeta potential of -45.4 mV. Increase of 219.72 % more stable compared to pure ZnO nanofluid. Pure ZnO nanofluid showed viscosity increment which could because of the sedimentation of nanoparticle occurs. Lower viscosity of surface modified ZnO nanofluid might due to SDS surfactant.

Rheological behavior of water and ethylene glycol based nanofluids containing oxide nanoparticles

The paper presents the results of experimental study of rheological behavior of nanofluids based from consideration of several tens of nanofluids based on water, ethylene glycol and engine oil, containing particles of different oxides and diamond. The sizes of nanoparticles ranged from 5 to 150 nm, while their volume concentration ranged from 0.25 to 8%. At that, no dispersants were used when preparing tested nanofluids. It is shown that in some cases, when increasing nanoparticle concentration, rheological behavior of nanofluids becomes non-Newtonian and is well described by power-law fluid models or Herschel–Bulkley fluids. The influence of nanoparticle size and material, as well as the nature of the base fluid on the rheological behavior of nanofluids have been studied.

An experimental determination and accurate prediction of dynamic viscosity of MWCNT(%40)-SiO2(%60)/5W50 nano-lubricant

In the current research, dynamic viscosity of MWCNT(%40)-SiO2(%60)/5W50 nano-lubricant were investigated experimentally. Dynamic viscosity of Nano-lubricant was measured at temperature range of 5°C–55°C, solid volume fraction between 0% and 1%, and fluid shear rate from 50 to 800rpm. Study on rheological behavior of nanofluid against shear stress showed that the nanofluid has non-Newtonian behavior. For presenting a relation between relative dynamic viscosity and independent parameters two methods were employed that are: artificial neural network and mathematical correlation. Results showed that, proposed correlation can estimate the value of relative dynamic viscosity with an acceptable accuracy. As an example the coefficient of determination (R-squared) was 0.9914, which represents a desirable value. An artificial neural network (ANN) for relative viscosity based on obtained data using the multi-layer perceptron (MLP) algorithm was designed. The results showed that the neural network with the appropriate instruction can estimate accurate value for dynamic viscosity.

Rheological behavior of mechanically stabilized and surfactant-free MWCNT-thermal oil-based nanofluids

The viscosity of nanofluids is one of the important parameter for the design of heat transfer processes. The evolution of usage of nanofluids in heat transfer processes is gaining more industrial consideration due to excellent thermal properties. However, limited attention is focused on the rheological behavior of nanofluids as of today. The multiwall carbon nanotubes (MWCNTs) are stabilized in thermal oil using ultrasonication and high stability is observed. The rheological behavior of thermal-oil based dispersant-free nanofluids are studied at varying high shear rates (100–2000s−1), temperatures (25–90°C) and nanoparticle concentrations (0.1–1wt%). The effect on the shear stress and viscosity by the addition of carbon nanotubes in thermal oil is discussed. The measured effective viscosity is compared with different theoretical conventional models. A significant increment in relative viscosity is observed at high concentrations of carbon nanotubes. A correlation is developed based on the temperature, nanomaterial concentration, and shear rate.

Predicting the effective viscosity of nanofluids for the augmentation of heat transfer in the process industries

Abstract Effective viscosity is helpful for the thermal design tasks in process industries, especially those related to pumping devices. Therefore, rheological behavior of nanofluids is important from power consumption point of view. In this study, an artificial neural network (ANN) model is developed to predict the effective viscosity of nanofluids based on a high number of experimental data available in the literatures. The effects of temperature, nanoparticle volume fraction, and the size of nanoparticles on the dynamic viscosity of nanofluids determined over wide ranges of operating conditions. The results indicate that the presented model can accurately predict the dynamic viscosity of nanofluids compared to the most important models for the dynamic viscosity of nanofluids. Eight different types of nanofluids, namely, Al 2 O 3 –water, CuO–water, TiO 2 –water, SiC–water, MWCNT–water, Fe 3 O 4 –water, Ni–water, and Ag–water are used to evaluate the accuracy of the proposed ANN model. The predicted effective dynamic viscosities of the nanofluids are in excellent agreement with experimental data with the AAD of 6.66% and R 2 -value of 0.9842.

Design and Evaluation of Carbon Nanotube Based Nanofluids for Heat Transfer Applications

ABSTRACTThe present work investigates the fabrication, thermal conductivity (TC) and rheological properties of water based carbon nanotubes (CNTs) nanofluids (NFs) prepared using a two-step method. As-received (AR) CNTs heated and the effect of heat treatment was studied using X-ray diffraction and thermogravimetric analysis. The AR-CNTs and heat-treated CNTs (HT-CNTs) were dispersed with varying concentration of surface modifiers Gum Arabic (GA) and TritonX-100 (TX) respectively. It was found that heat treatment of CNTs effectively improved the TC and influenced rheological properties of NFs. Scanning electron microscopy analysis revealed TX modified NFs showed better dispersion ability compared to GA. Surface modification of the CNTs was confirmed by Fourier Transformation Infrared (FTIR) analysis. Zeta potential measurement showed the stability region for GA modified NFs in the pH range of 5-11, whereas pH was between 9.5-10 for TX NFs. The concentration of surface modifier plays an extensive role on both TC and rheological behavior of NFs. A maximum TC enhancement of 10% with increases in viscosity around 2% for TX based HT-CNTs NFs was measured. Finally comparison of experimental TC results with the predicted values obtained from a model demonstrated inadequacy of the predictive model for CNT NFs system.