Transport Properties Of Nanofluids Research Articles

Analysis of thermophysical and transport properties of nanofluids using machine learning algorithms

Accurate calculations of thermophysical properties (TPP) and fluid transport properties are crucial for solving and enhancing a myriad of heat and mass transfer issues, particularly in the field of engineering and associated disciplines. This is even more significant in the case of advanced fluids, such as nanofluids, which play a pivotal role in the progression of new technologies. The significance of TPP in heat transfer studies is undeniable, yet there is a notable scarcity of reliable TPP values for nanofluids that can be uniformly applied to numerous problems and complex industrial systems. This shortage poses a unique challenge for nanofluids. The current study introduces NanoFluid Explorer (NanoFEx), a comprehensive MATLAB-based database specifically designed to catalog the TPP of nanofluids. The database is divided into two main parts. The first part employs Gaussian regression, supported by experimental data derived from existing literature, using kernel functions commonly used for this type of analysis. The second part features a neural network, designed for efficiency, that is trained on the aforementioned database and supplemented by an additional database formed from the Gaussian-regression output. This setup allows NanoFEx to recapture TPP values for nanofluids that may be absent in the existing literature. The preliminary findings demonstrate that NanoFEx could prove to be an invaluable resource for both theoretical and experimental researchers studying heat and mass transfer in nanofluids. Moreover, NanoFEx confirms thermodynamically consistent values with any discrepancies attributed to finite-precision computations. Furthermore, NanoFEx achieved over 93% accuracy in predicting key properties. The novelty and relevance of this study stem from the comprehensiveness of the experimental results database. In summary, this research provides an extensive and, to the best of the authors' knowledge, the most reliable dataset currently available for TPP of nanofluids. This significant contribution aims to unify nanofluid TPP research and optimize experimental processes while setting a crucial standard for future nanofluid applications.

A new relationship on transport properties of nanofluids. Evidence with novel magnesium oxide based n-tetradecane nanodispersions

The worldwide increasing of thermal energy consumption fosters new technological solutions based on nanomaterials. The use of nanofluids enhances energy efficiency leading to eco-friendlier devices. Thus, researchers are encouraged to understand how modified thermophysical properties improve heat transfer capability. Magnesium oxide based n-tetradecane nanofluids are designed in terms of stability for cold storage application. Thermal conductivity, viscosity, density, and isobaric heat capacity were determined by transient hot wire, rotational rheometry, mechanical oscillation U-tube, and differential scanning calorimetry. Furthermore, a useful relationship on thermal conductivity and viscosity of nanofluids is proposed based on Andrade, Osida and Mohanty theories. Its reliability is checked with the here reported results and literature data of different nanofluids: titanium oxide within water, silver within poly(ethylene glycol), and aluminium oxide within (1-ethyl-3-methylimidazolium methanesulfonate + water). Similar trends have been found for all nanofluids excepting titanium oxide aqueous nanofluids, this differentiated behaviour being expected by the proposed relationship.

Using molecular dynamics simulations to investigate the effect of the interfacial nanolayer structure on enhancing the viscosity and thermal conductivity of nanofluids

To understand the remarkable enhancements in viscosity and thermal conductivity of nanofluids, a molecular dynamics (MD) simulation approach was used to investigate the structure and thickness of the interfacial layer and obtain values for radial distribution function, g(r), viscosity, and thermal conductivity of Cu/water nanofluids with volume fractions and temperatures ranging from 0.5–2 vol% and 293–333 K, respectively. The results revealed that value of g(r) was much higher in the first molecular nanolayer compared to the second layer, indicating that greater numbers of water molecules are present in the first layer, which reduces contact thermal resistance and improves thermal conductivity of nanofluids. Moreover, while value of g(r) increased with increasing Cu volume fraction and decreased with temperature, nanolayer thickness was unchanged with temperature at each volume fraction, indicating that intermolecular forces intensify in the first nanolayer. Macroscopically, viscosity and thermal conductivity of the nanofluids increased at higher volume fractions, showing increases of 71.7% and 75% for viscosity, and 41.7% and 53.3% for thermal conductivity at 0.5 and 2 vol%, respectively, compared to water at 333 K. These results, although obtained for Cu/water systems, can provide useful insights into structural and transport properties of nanofluids in general.

Transport properties of nanofluids and applications

Transport properties of nanofluids and applications

Influence of Al2O3 nanoparticles on the stability and viscosity of nanofluids

Improving the performance of heat transfer fluids is becoming significantly important. One of the most effective methods for increasing thermal conductivity is the addition of solid nanoparticles to fluids. The molecular dynamics simulation method has the proper ability to diagnose the stability of fluids. This method can be used with a view to the low cost and high repeatability as a suitable method for studying different materials. In this study, the stability and viscosity of the nanofluid at different percentages of base fluid [water–ethylene glycol (EG)] in contact with Al2O3 nanoparticles, was investigated by molecular dynamics simulation with using some analyzes such as total energy, kinetic energy, radial distribution function diagrams and dispersion diagrams. The results show that, the stability of Al2O3 is better where the percentage of water in the base fluid is higher. The molecular dynamics simulation properly predicts the nanofluid viscosities in all concentrations, temperatures and for each base fluid. The maximum discrepancy between experimental and simulation results is 15.1% at 40 °C for 0.5% Al2O3 nanoparticles in the water–EG (60:40) mixture. The obtained results can provide useful understanding of the structural and transport properties of nanofluids, not only in the EG–water nanofluids, but also in other types of nanofluids.

Nanoparticle transport phenomena in confined flows.

Nanoparticles submerged in confined flow fields occur in several technological applications involving heat and mass transfer in nanoscale systems. Describing the transport with nanoparticles in confined flows poses additional challenges due to the coupling between the thermal effects and fluid forces. Here, we focus on the relevant literature related to Brownian motion, hydrodynamic interactions and transport associated with nanoparticles in confined flows. We review the literature on the several techniques that are based on the principles of non-equilibrium statistical mechanics and computational fluid dynamics in order to simultaneously preserve the fluctuation-dissipation relationship and the prevailing hydrodynamic correlations. Through a review of select examples, we discuss the treatments of the temporal dynamics from the colloidal scales to the molecular scales pertaining to nanoscale fluid dynamics and heat transfer. As evident from this review, there, indeed has been little progress made in regard to the accurate modeling of heat transport in nanofluids flowing in confined geometries such as tubes. Therefore the associated mechanisms with such processes remain unexplained. This review has revealed that the information available in open literature on the transport properties of nanofluids is often contradictory and confusing. It has been very difficult to draw definitive conclusions. The quality of work reported on this topic is non-uniform. A significant portion of this review pertains to the treatment of the fluid dynamic aspects of the nanoparticle transport problem. By simultaneously treating the energy transport in ways discussed in this review as related to momentum transport, the ultimate goal of understanding nanoscale heat transport in confined flows may be achieved.

Importance of nanolayer formation in nanofluid properties: Equilibrium molecular dynamic simulations for Ag-water nanofluid

Most of the researches have authenticated the irrefutable role of interfacial nanolayer in molecular level. Understanding the mechanism of interfacial nanolayer effect on macroscopic fluid properties is of crucial importance. Thus, this study is aimed to examine the effect of nanolayer on two important nanofluid properties, i.e. density and viscosity, by performing extensive molecular dynamics simulations. It was found that, the formation of the ordered liquid nanolayer caused contraction of base fluid. The nanofluid was considered as a three-component mixture, i.e. nanoparticle, base fluid after mixing with nanoparticles and nanolayer. Accordingly, a new ternary mixture relation was proposed to compute the nanofluid density. Obtained results revealed the importance of nanolayer effect on density of nanofluids. Moreover, the role of liquid layering in nanofluid viscosity was analyzed. The obtained results can provide useful understanding on the structural and transport properties of nanofluids not only in the Ag-water nano-colloid, but also in other types of nanofluids.

Experimental Study of Copper Nano-fluid on Thermosyphons Thermal Performance

A new way to remove the intense heat by developing and implementing an innovative low cost compact loop thermosyphon has been widely observed. Especially, it was concluded that nano-fluids are potential heat transfer fluids to be used as working fluid in thermosyphon. Therefore, the thermophysical or transport properties of nano-fluids in thermosyphon need to be discussed. In present work was to experimental study the thermal performance of thermosyphon using a copper nano-fluid as a working fluid. The experiment was performed in order to measure the temperature distribution and compare heat transfer rate of the thermosymphon with nano-fluid and with pure water. The concentration of copper nano-particle was 10, 30 and 50 ppm. The tested working temperature was 60, 70 and 80C. Results shown that the concentration of 50 ppm of copper nano-fluid improved thermal performance compared with the case of pure water. The optimum and behavior of copper nano-fluid in thermosyphon is presented, which highlights all of the beforehand mentioned advantages.

Simulation studies on the transport properties of Cu-H2O nanofluids based on water continuum assumption

Nanofluid is a kind of new engineering medium which is created by dispersing small quantity of nano-sized particles in the base fluid. The dispersion of solid nanoparticles in conventional fluids changes their transport properties remarkably. Molecular dynamics simulation (MDS) is an important approach to study the transport properties of nanofluids. However, the computation amount is huge, and it is very difficult to use the normal MDS to capture the transient flow and heat processes in Cu-H2O nanofluids if the regions in the simulation reach 149.6443 nm3 or 299.2883 nm3, and the number of Cu nano-particles reaches 6-64. Further study by means of simulation on the effects on effective transport properties of nanofluids is also difficult. In this paper, the water-based fluid region of 149.6443 nm3 or 299.2883 nm3 is assumed as continuum phase because of the very low Knudsen number of fluid, and the effects of water on nano-particles are fitted into the Cu-Cu potential parameters. Using the proposed method, the computation amount is significantly reduced. The effective thermal conductivity and dynamic viscosity coefficient of Cu-H2O nanofluids under the stationary condition are simulated and the results are verified with existing experimental data. The motion and aggregation processes of nano-particles in the water-based fluids at different velocity shear rate are simulated. Effects of velocity shear rate, fluid velocity, temperature gradient, and average temperature on the effective thermal conductivity and the dynamic viscosity of Cu-H2O nanofluids in the processes of flow and heat transfer are studied. Three conclusions can be drawn from the obtained results. Firstly, the proposed method is feasible to capture the transient flow and heat processes in Cu-H2O nanofluids, and is also capable to further study the transport properties of Cu-H2O nanofluids. Secondly, the velocity shear rate acting on a nanofluid can effectively prevent the aggregating process of nano-particles, and therefore reduce the diameter of particle-aggregations. Finally, the velocity shear rate and the average temperature of Cu-H2O nanofluids have much more effects on the transport properties, while the fluid velocity and temperature gradient have less effects; the velocity shear rate increases the effective thermal conductivity of a nanofluid but decreases its dynamic viscosity. A rise of average temperature increases the effective thermal conductivity but decreases the dynamic viscosity.

Transport properties of nanofluids. A critical review

Transport properties of nanofluids. A critical review

Viscosity of Nanofluids. Why It Is Not Described by the Classical Theories

Transport properties of nanofluids are extensively studied last decade. This has been motivated by the use of nanosized systems in various applications. The viscosity of nanofluids is of great significance as the application of nanofluids is always associated with their flow. However, despite the fairly large amount of available experimental information, there is a lack of systematic data on this issue and experimental results are often contradictory. The purpose of this review is to identify the typical parameters determining the viscosity of nanofluids. The dependence of the nanofluid viscosity on the particles concentration, their size and temperature is analyzed. It is explained why the viscosity of nanofluid does not described by the classical theories. It was shown that size of nanoparticles is the key characteristics of nanofluids. In addition the nanofluid is more structural liquid than the base one.

Effect of temperature on volumetric and transport properties of nanofluids containing ZnO nanoparticles poly(ethylene glycol) and water

The nanoparticles of ZnO have been dispersed in base fluids of poly(ethylene glycol), PEG, and its aqueous solutions. Stability of these nanofluids has been verified with UV-Vis spectroscopy. Dynamic light scattering and size analyze laser methods were used to obtain particle size of the nanofluids investigated. The density, speed of sound and viscosity values for these nanofluids have been measured at T=(293.15,298.15,308.15 and 318.15)K. From these experimental data, the excess molar volume, VmE and isentropic compressibility, κs, have been determined. The behaviour of these values with temperature and concentration has been interpreted for clarifying the dispersion of ZnO nanoparticles in PEG and aqueous solution of PEG. The effects of ZnO nanoparticles and temperature have also been investigated on volumetric and transport properties of aqueous solutions of PEG. The VmE, was adequately fitted to the Redlich–Kister, Ott et al. and Singh et al. equations. The isentropic compressibility values were correlated with the polynomial equation. The Eyring-NRTL and Eyring-mNRF models have successfully been used for correlating the viscosity values of the nanofluids investigated with temperature dependency considered. The performance of the Einstein, Brinkman, Lundgren and Batchelor models in the prediction of viscosity values of the (ZnO+PEG) nanofluid has also been tested.

Investigation of a nanofluid-cooled microchannel heat sink using Fin and porous media approaches

The present paper focuses on analytical and numerical study on using nanofluids as coolant of a microchannel heat sink. The nanofluid studied in this paper is made from copper oxide (CuO) and water. Two common analytical approaches are used: the Fin model and the porous media approach. The Fin model is based on the assumption of uniform fluid temperature in the direction normal to the fluid flow which causes inaccuracy in the predictions of this approach. On the other hand, modified Darcy equation for the fluid and two-equation model for heat transfer between fluid and solid sections are employed in porous media approach. In addition, to deal with nanofluid heat transfer, a model based on Brownian-motion of nanoparticles is used. The model evaluates the thermal conductivity of nanofluid considering the thermal boundary resistance, nanoparticle diameter, volume fraction and the fluid temperature. This model is included in heat transfer equations of the two approaches, and the velocity profile is obtained analytically considering the transport properties of nanofluids. Firstly, the effects of particle volume fraction and Brownian–Reynolds number on temperature distribution and overall heat transfer coefficient are investigated. After that, the influence of different channel aspect ratios and porosities are studied. Both approaches are considered and compared in details. Furthermore, an optimum aspect ratio is found to minimize the friction factor in different Reynolds numbers.

Nanoparticle Friction Force and Effective Viscosity of Nanosuspensions

The transport properties of nanofluids are investigated by the molecular dynamics method. It is shown that the force acting on a nanoparticle is nonstationary, in contrast to the Stokes force. In the initial stage of relaxation, the friction force is greater than the Stokes value. Subsequently, this force decreases and reaches an asymptotic value. This value is comparable to the Stokes force only for a massive particle. A correlation for determining the friction coefficient is constructed. It is established that the effective viscosity coefficient of nanofluids depends not only on the volume concentration of nanoparticles but also on the nanoparticle mass and radius.

Dynamic structure and cluster formation in confined nanofluids under the action of an external force field

The dynamic structure and the formation of clusters in nanoparticle colloidal solutions (nanofluids) confined between two parallel walls and submitted to the action of an external force field is studied by extensive Brownian-dynamics simulations. The self-correlation of individual particles and the time correlation between distinct particles are analyzed by calculating the density-density time correlation (van Hove) function. It is shown that the self-diffusion is reduced by the external force field while the lifetime of collective modes of nanoparticles (i.e., natural phonons) is significantly enhanced by this force. We demonstrate that this result is related to disorder-order transitions in the nanoparticle spatial distribution under perturbation. Interestingly, we highlight that the interaction forces mediated by the walls act like repulsive interparticle forces. They tend to increase the structural disorder and to lower the lifetime of collective modes. Our results suggest that the heat transport properties of nanofluids could be actively controlled in nanometer-size systems.