Thermal Characteristics Of Nanofluids Research Articles

Thermal transport of radially magnetized peristalsis of non-Newtonian nanofluid through an asymmetric curved channel

Present examination explores the heat and mass transfer phenomena for magnetohydrodynamics (MHD) peristaltic transport of diethylene glycol (DEG)-based Cross nanofluid through an asymmetric curved channel. The mass and thermal characteristics of nanofluid are established through the assessment of Buongiorno nano-liquid model, which allows to identify intriguing features of thermophoretic and Brownian diffusion coefficients. Further, velocity slip conditions are enforced on the peristaltic walls. The influences of thermal radiation, radius-dependent magnetic field and viscous dissipation are also taken into consideration. The governing equations are simplified by employing lubrication theory (“biological estimate of the creeping transportation phenomenon”), and resulting system is tackled numerically. Impacts of different flow parameters on the nanofluid’s velocity, nanomaterials concentration profile, heat and mass transfer, streamlines, temperature of nanofluid, and stresses at the wall are analyzed via graphs and tables. The findings of this investigation report that nanofluid’s temperature enhances against Hartmann and Brinkman numbers, whereas it declines for the thermal radiation parameter. The distribution of the concentration profile decreases for Brownian motion while it increases for the thermophoresis parameter. Further, a development in the stresses, thermal and mass transfer rates at the boundary is seen for better values of the Hartmann number. Additionally, higher values of the velocity slip parameter show increasing behavior for the velocity of nanofluid near the walls of the channel. The effects of MHD with magnesium aluminate nanoparticles suspended in DEG base fluid-based nanofluid through an asymmetric curved conduit have many uses in industry, organic compounds, biomedical engineering, and commercial productions, such as brake fluid, tobacco, polyester resins, certain dyes, printing ink, polyurethanes, glue, resins, antifreeze, nitrocellulose, oils, cigarettes, plasticizers, and so forth. DEG-based nanofluids are also used in human medications, including acetaminophen and sulfanilamide, which can result in incidents of human poisoning, some of which have been fatal, either intentionally or unintentionally.

Thermal examination for the micropolar gold–blood nanofluid flow through a permeable channel subject to gyrotactic microorganisms

Presently, scientists across the world are carrying out theoretical and experimental examinations for describing the importance of nanofluids in the heat transfer phenomena. Such fluids can be obtained by suspending nanoparticles in the base fluid. Experimentally, it has proved that the thermal characteristics of nanofluids are much better and more appealing than those of traditional fluids. The current study investigates the heat transfer for the flow of blood that comprises micropolar gold nanoparticles. The influence of chemically reactive activation energy, thermophoresis, thermal radiations, and Brownian motion exists between the walls of the channel. A microorganism creation also affects the concentration of nanoparticles inside the channel. Suitable transformation has been used to change the mathematical model to its dimensionless form and then solve by using the homotopy analysis method. In this investigation, it has been revealed that the linear velocity behavior is two-folded over the range 0≤η≤1. The flow is declining in the range 0≤η≤0.5, whereas it is augmenting upon the range 0.5≤η≤1. Thermal characteristics are supported by augmentation in volumetric fraction, thermophoresis, radiation, and Brownian motion parameters while opposed by the Prandtl number. The concentration of the fluid increases with augmentation in activation energy parameters and decays with an increase in thermophoresis, Brownian motion, chemical reaction parameters, and the Schmidt number. The density of microorganisms weakens by growth in Peclet and bioconvection Lewis numbers.

A novel design for solar collector used for water heating application having nanofluid as working medium: CFD modeling and simulation.

A solar collector is a simple and cheap device that converts solar radiation into valuable heat energy. The thermal performance of the solar collectors can be enhanced significantly with the suspension of nanoparticles in the base fluid. A novel design for a solar-assisted water heater (SWH) is proposed in the current study, and the effect of nanofluid has been investigated on the thermal efficiency of the SWH. The use of nanofluid is one of the prominent methods in comparison to other techniques for improving the performance of solar collectors. Therefore, the base working fluid, i.e., water is mixed with the alumina nanoparticles of average particle size of 30nm, and they are assumed to be spherical. The flow and thermal characteristics of nanofluid through the solar water heater are simulated numerically with the help of the Eulerian-Eulerian two-phase model using the finite volume method (FVM). The commercial package ANSYS Fluent, is used for modeling the problem under transient conditions with a pressure-based solver. In comparison to a conventional flat plate collector, the proposed solar water heater consists of a corrugated absorber-plate and the effect of the radius of curvature has been investigated on the heat transfer and collector efficiency. With the proposed design, the heat transfer area available with the riser tubes increases remarkably and it leads to a 43% and 14% increase in heat transfer augmentation and collector efficiency, in comparison to the conventional solar water heater.

Study on Nanoparticle Agglomeration During Chemical Mechanical Polishing (CMP) Performance

The materials used in base fluids and nanoparticles are varied. One- and two-step manufacturing processes are used to create stable and highly conductive nanofluids. Both methods for making nanoparticle suspensions suffer from nanoparticle agglomeration, which is a major problem in any technique that uses nanopowders. As a result, the key to substantial surface finishing at planarization treatments and increase in the thermal characteristics of nanofluids is the production and suspension of almost non-agglomerated or monodispersed nanoparticles in liquids. This unfavorable aggregation is a major problem in nanopowder technology. Primary material constituents agglomerate rapidly overcoming the stable situation, and nanoparticle agglomerates set out in liquids, making it difficult to create nanofluids using two-step techniques. This research looks at the link between nanoparticle agglomeration during slurry flow and Material Removal Rate (MRR) during chemical mechanical polishing (CMP). The reciprocal relationship between MRR and the shear force exerted by the slurry flow was qualitatively elucidated by the researchers for the theoretical investigation. However, the present manipulation is focused on quantifying the shear stress exerted by nanoparticles floating in the slurry. As a result, the MRR-aggregation model is established based on the relationship between MRR and shear force. The experiment is being carried out to support this idea. The experimental results of aggregation and shear forces have been conducted by some recent studies. However, the extension to the real CMP is very promising for accomplishing a precise style of the removal mechanism and surface finishing criterion as well.

Thermal and hydrodynamic behavior of suspensions comprising nano-encapsulated phase change materials in a porous enclosure

Nano-encapsulated phase change materials (NEPCMs) are known to enhance the thermal characteristics of fluids; therefore, there is a rising interest in employing these materials in future thermal control systems. This paper investigates hydrodynamic and thermal characteristics of nanofluids, NEPCMs mixed in the host liquid, in glass balls as a porous structure. The geometry is a two-dimensional porous square cavity in which the left boundary is hot, the right boundary is cold, and the horizontal ones are considered to be insulated. The NEPCMs are composed of polyurethane (PU) as shell and nonadecane as a core. The impact of different non-dimensional parameters, such as Darcy number, 10−5 ≤ Da ≤ 10−1, porosity, 0.4 ≤ ɛ ≤ 0.9, Stefan number, 0.2 ≤ Ste ≤ 100, fusion temperature, 0 ≤ θf ≤ 1, and volume fraction of the NEPCMs, 0 ≤ ϕ ≤ 0.05, is studied on the flow and heat transfer characteristics. It is shown that the volume fraction of NEPCMs is directly proportional to the strengthening of the heat transfer rate in such a way that applying 5% volume fraction of NEPCMs could enhance the heat transfer up to 20.1% and 14.1% at θf = 0.5 in comparison to the cases of pure fluid and NEPCM mixture with no core-phase change, respectively. The effect of non-dimensional fusion temperature on the rate of heat transfer is also found to be noticeable. The maximum average Nusselt number emerges at θf = 0.5, which is the optimum fusion temperature.

Multiscale modelling of ceramic nanoparticle interactions and their influence on the thermal conductivity of nanofluids

There is currently a lack of a reliable theory capable of making accurate predictions of the thermal enhancement in nanofluids (with relatively low solid volume fractions). The work described therefore assesses the thermal conductivity of nanoparticle suspensions in fluids using a Lagrangian particle tracking-based computational modelling technique. A 3D, multiphase fluid-solid model is developed which predicts the motion of suspended nanoparticles. The nanofluid is predicted using an Eulerian-Lagrangian hybrid approach with a constant timestep. This technique takes various multiscale forces into consideration in the calculations, whose characteristic scales are quite different, providing for the first time an analysis of all factors affecting the stability and thermal conductivity of nanofluids. The system considered consists of 71 nm diameter Al2O3 ceramic nanoparticles suspended in water, with homogeneous temperature distributions ranging from 25 °C to 85 °C, at various volume fractions between 1% and 5%. The results of the simulations demonstrate the effectiveness of the presented technique, with predictions elucidating the role of Brownian motion, fluid viscous drag, inter-particle collisions and DLVO attraction and repulsion forces on nanofluid stability. Results indicate that aggregated nanoparticles formed in the suspensions, at various particle concentrations, play an important role in the thermal behaviour of the nanofluids. Predictions are in agreement with theoretical and experimental results obtained in related studies. The thermal characteristics of nanofluids are also considered as a function of temperature, system chemistry and time (measured from an initially homogeneously dispersed state). The proven enhancement in the conductivity of fluids affected by the addition of nanoparticles has great potential to assist the development of commercial nanofluid technology aimed at energy efficient and sustainable processes.

Effects of Fe3O4/Water Nanofluid on the Efficiency of a Curved Pipe

Different-radius of curvature pipes are experimentally investigated using distilled water and Fe3O4–water nanofluid with two different values of the nanoparticle volume fraction as the working fluids. The mass flow rate is approximately varied from 0.2 to 0.7 kg/min (in the range of laminar flow); the wall heat flux is nearly kept constant. The experimental results reveal that utilizing the nanofluid increases the convection heat transfer coefficient and Nusselt number in comparison to water; these outcomes are also observed when the radius of curvature is decreased and/or the mass flow rate is increased (equivalently, a rise in Dean number). The resultant pressure gradient is, however, intensified by an increase in the volume concentration of nanoparticles and/or by a rise in Dean number. For any particular working fluid, there is an optimum mass flow rate, which maximizes the system efficiency. The overall efficiency can be introduced to include hydrodynamic as well as thermal characteristics of nanofluids in various geometrical conditions. For each radius of curvature, the same overall efficiency may be achieved for two magnitudes of nanofluid volume concentration.

Effectiveness of various shapes of Al2O3 nanoparticles on the MHD convective heat transportation in porous medium

The influences of Al2O3 nanoparticles with various shapes on thermal characteristics of nanofluid within a permeable space concerning magnetic force have been simulated by means of CVFEM. To form the final PDEs, radiation term has been incorporated. Impacts of magnetic force, radiation constraint, Rayleigh number and shape factor on nanomaterial behaviour have been analysed. Results demonstrate that the higher values of shape factor lead to augmented convective heat transfer. By augmenting the magnetic strength, conductive heat transfer can be predominant than that of the convection.

Modern developments about statistical declaration and probable error for skin friction and Nusselt number with copper and silver nanoparticles

This communication explores simultaneous impact of Joule heating and viscous dissipation in radiative flow of viscous fluid by a stretching cylinder. The thermal characteristics of nanofluids are explored using copper and silver nanoparticles. Homogeneous and heterogeneous reactions are accounted. Statistical declaration and probable error for skin friction and Nusselt number are computed. The nonlinear differential systems are solved using Euler’s Explicit Method (EEM). The effects of emerging variables for velocity, temperature, concentration, skin friction and Nusselt number are examined extensively. It is noticed that the magnetic parameter decays the fluid velocity for copper-water and silver-water nanomaterials. Radiative heat transfer and viscous dissipation lead to an increase in the fluid temperature and thermal boundary layer thickness.

Numerical investigation and optimization of flow and thermal characteristics of nanofluid within a chaotic geometry

In this study, hydrothermal characteristics of the water–TiO2 nanofluid are evaluated in the rectangular C-shaped chaotic channel by applying the two-phase Euler–Lagrange method. The results show that the fluid temperature distribution in the C-shaped channel is much more uniform than that in the straight rectangular channel due to the intense mixing in the chaotic geometry. By increasing the concentration and reducing the particle size, both convective heat transfer and pressure drop increase in the chaotic channel. For finer particles, due to more intense particle migration related to the Brownian motion, more uniform concentration distribution is obtained at the channel cross section. The model of mean convective heat transfer coefficient and pressure drop in terms of concentration and particle size was developed by neural network. In order to obtain some cases of the variables (i.e. size and concentration of nanoparticles) in which maximum heat transfer along with minimum pressure drop occurs, optimization on neural network model was implemented using methods of two-objective as well as single-objective (i.e. genetic algorithm coupled with compromise programming decision making method). Eventually, optimum cases were suggested for different importance levels of objective functions.

An experimental study on thermal characteristics of nanofluid with graphene and multi-wall carbon nanotubes

High-thermal conductivity enhancement of nanofluid is one of the promising topics of the nanoscience research field. This work reports the experimental study on the preparation of graphene (GN) and multi-walled carbon nanotubes (MWCNTs) based nanofluids with the assistance of sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS) surfactants, and their thermal behaviors. The present work suggests not a solution, but a solution approach and deduces a new conclusion by trying to resolve the agglomeration problem and improve the dispersibility of nanoparticles in the base fluid. The analysis results of FESEM, thermal conductivity, diffusivity, effusivity and heat transfer coefficient enhancement ratio of nanofluid with surfactants SDS and SDBS expose strong evidence of the dispersing effect of surfactant on the making of nanofluid.

Entropy generation of nanofluid flow with streamwise conduction in microchannels

The effect of streamwise conduction on the entropy generation of low-Peclet-number nanofluid flow in circular microchannel heat sinks under exponentially decaying wall heat flux with constant pumping power condition is analytically studied. Mathematical models with and without streamwise conduction term in the energy equation are developed and closed-form solutions are obtained. Due to the dramatic increase in the effective thermal conductivity of nanofluids, the streamwise conduction effect is justified to be more significant in the nanofluids compared to their base fluids. The significance of the streamwise conduction which is prevalent in low-Peclet-number flow regime is greatly amplified when the volume fraction of nanoparticle is increased. The thermal characteristics of nanofluids are prominently affected due to the presence of streamwise conduction which consequently alters the characteristics of entropy generation in the second-law analysis. Significant deviations are observed when comparing the cases with and without streamwise conduction. Minimal entropy generation is identified in certain range of the low-Peclet-number flow regime, providing an ideal operating condition from the second-law aspect for nanofluid flow in microchannels. The exergetic effectiveness is also investigated based on the variations on the volume fraction of nanoparticle suspension and the microchannel aspect ratio.

Stability of Nanofluids

It has long been established that a suspension of nanosized solid particles in liquids provide useful advantages in industrial heat transfer fluid systems. Numerous investigations on nanofluids show a significant enhancement in thermal conductivity over the base fluid in which these nanoparticles are dispersed. However, the stability of the suspension is critical in the development and application of these new kind of heat transfer fluids. Rather, high discrepancy in the published data for the same nanoparticles on the physical and thermal characteristics of nanofluids is primarily due to different methods adopted by different researchers to obtain stable nanofluids. Sedimentation and agglomeration of nanoparticles in nanofluids and their dispersion stability has not been well addressed in the literature. Hence, there is a need to establish a standard method of preparation of these nanofluids so as to obtain a unified data which can eventually be utilized for the application of nanofluids. This chapter focuses on the stability of nanofluids prepared via two step process. Different parameters that affect the stability of nanofluids have been discussed. Different techniques that have been used for the evaluation of the stability characteristics of nanofluids have been elucidated.

Silicon oil based multiwalled carbon nanotubes nanofluid with optimized thermal conductivity enhancement

Multiwalled carbon nanotubes (MWNTs) were treated by concentrated acid combined with mechanical ball mill technology. The treated multiwalled carbon nanotubes (TCNTs) with functionalized surfaces and controlled morphologies were used to prepare silicon oil based nanofluids by using hexamethyldisiloxane as dispersant. Thermal conductivity results of the obtained nanofluids show that the collective effects, involving straightness ratio, aspect ratio, and aggregation of TCNTs, play a key role in the thermal conductivity of CNT nanofluids. This study suggests that the thermal characteristics of nanofluids might be manipulated by means of controlling the morphology of the additions, which also provide a promising way to conduct investigation on the mechanism of heat transfer in nanofluids. Reliable rheological properties of the prepared nanofluids were provided. It is important when the nanofluids are used in the potential heat exchange areas. The silicone oil based fluids behave in Newtonian manner in all the studied MWNT volume fractions and temperatures. The hexamethyldisiloxane added in silicone oil, in addition to decreasing the silicone oil viscosity, has little effect on the nanofluid rheological properties.

Theoretical Model Development for Nanofluids Thermal Effectiveness

Heat transfer fluids play an important role in many industrial sectors. However, the low heat transfer characteristics of conventional fluids obstruct the performance enhancement and the high compactness of heat exchangers. In order to improve thermal characteristics of the conventional fluids, nanofluids are prepared by adding multi walled carbon nanotubes (CNTs) with base fluids. Though different experimental studies on nanofluids are available, theoretical models are also needed to predict its thermal behaviour. This work intends to address dimensional analysis using the Buckingham Pi theorem to develop an empirical model for predicting thermal characteristics of nanofluids. The latter will be achieved through the use of operational variables and physical properties for the identification of detrimental factors which eventually lead to the thermal enhancement of nanofluids. It can be observed from this analysis that volume fraction and temperature of the nanofluids are the most influencing parameters on the nanofluids thermal conductivity. In what concerns heat transfer coefficient, it is the velocity of the nanofluid that plays a critical role apart from the afore mentioned two parameters. Therefore it is believed that by controlling these parameters, the thermal effectiveness of the nanofluids can be established.