Different Volume Fractions Of Nanoparticles Research Articles

Computational modeling of porous medium inside a channel with homogeneous nanofluid

In the present study, the flow field and heat transfer have been simulated numerically inside a channel. The channel is under the constant heat flux. The main objective of this research is investigating the effect of the arrangement of the porous medium in water/Al2O3 nanofluid inside the channel on the flow and heat transfer characteristics. The effect of various arrangements of porous medium with two porosities and different volume fractions of nanoparticles has been investigated in a constant cross section of the porous medium. The results are validated with other references, and excellent consistency has been seen. The results show that using the porous medium has more effect on heat transfer than using nanofluid, and the arrangement of the porous medium has a strong influence on temperature profile and heat transfer. Based on the results, using stair arrangement of porous medium with the distance of 30 cm from each other and the length of 30 cm and using nanofluid with 0.02 volume fraction of Al2O3 nanoparticles have better performance than other considered arrangements.

An experimental study on heat transfer and fluid flow of rough plate heat exchanger using Al2O3/water nanofluid

ABSTRACTIn the present study, an experimental investigation of performance evaluation of plate heat exchanger (PHE) with the rough surface using AL2O3/water nanofluid was achieved. The experiments were developed for different surface roughnesses of 0.978 µm (smooth surface), 1.276 µm, 2.825 µm and 3.657 µm with different volume fractions of nanoparticles of 1.2 vol.%, 1.9 vol.% and 2.6 vol.% at Reynolds number of 500 ≤ Re ≤5000. The Nusselt number (Nu), the friction factor (f) and the heat transfer enhancement factor (HTEF) were estimated. The results show that increasing the volume fraction of nanoparticles and surface roughness enhances the heat transfer rate as well as increases the pressure drop in PHE. Hence, the influence of surface roughness is more considerable than that of volume fraction of nanoparticles on PHE performance. Furthermore, for smooth surface, the HTEF is improved by 2%, 3.7% and 5.4% for volume fraction of nanoparticles of 1.2 vol.%, 1.9 vol.% and 2.6 vol.%, respectively; while these values for the highest value of surface roughness, i.e., 3.657 µm, are 9.4%, 11.8% and 13.7%. Based on the experimental results, a new empirical correlation to predict Nu for base fluid is obtained with a maximum deviation of 2.87%.

Neutronic analysis of a VVER-1000 reactor with nanofluid as coolant through zeroth order average current nodal expansion method

Attempt is made to solve the two group diffusion equations for a typical VVER-1000 reactor with Al2O3 nanofluid coolant. Diffusion equations are discretized for a three dimensional hexagonal volume through zeroth order average current nodal expansion method (ZACNE). The cross sections are calculated for different volume fractions of nanoparticles in coolant by applying the WIMS-D5 code. Results indicate that by increasing the volume fraction of the Al2O3 nanoparticles in VVER-1000 reactor, the relative power distribution in the core center reduces and the distribution of power increases around the core. The effective multiplication factor decreases by an increase in the concentration of nanoparticles at the core of the reactor. The final results obtained by applying ZACNE codes, reveal that volume fraction of Al2O3 below 0.1% is the optimum for normal operation.

The unsteady flow of generalized hybrid nanofluids: applications in cementitious materials

Since the introduction of reinforced concrete as a structural material, the construction industry has made remarkable progress. The addition of nanoparticles will result in a stronger, more durable, self-healing, fire-resistant, easy to clean, and rapid compaction of the cementitious material. Some of the nanoparticles that could be used for these features are nano silica, aluminum oxide, nanostructured metals, carbon nanotubes, and carbon nanofibers (CNFs). In this article, the mathematical problem is modeled for hybrid nanofluids and generalized by using the concept of Caputo-Fabrizio fractional derivatives, and its application in the cementitious materials is studied theoretically. The problem is solved using the Laplace transform technique. The results show that by adding the Al2O3 nanoparticles and MWCNTs, the binding strength of the cement may be enhanced. Moreover, the effects of Al2O3 nanoparticles and MWCNTs are also discussed separately. Graphs are drawn for different volume fractions of nanoparticles and MWCNTs and discussed physically.

Effect of MHD on the flow and heat transfer characteristics of nanofluid in a grooved channel with internal heat generation

Purpose The purpose of this study is numerical simulation of magnetohydrodynamics (MHD) water–Al2O3 nanofluid mixed convection in a grooved channel with internal heat generation in solid cylinders. Simulations were carried out at Reynolds numbers 50 ≤ Re ≤ 100, Hartmann numbers 0 ≤ Ha ≤ 15, Grashof numbers 5,000 ≤ Gr ≤ 10−4 and volume fraction 0 ≤ φ ≤ 0.04. The effect of Reynolds number and the influence of magnetic field and pressure drop on convective heat transfer coefficient were studied in different volume fractions of nanoparticles at different Reynolds numbers. Design/methodology/approach The results show that average Nusselt number increases by increasing Reynolds and Hartman numbers. Also, when Hartman number increases, velocity profile becomes asymmetric. Pressure distribution shows that magnetic field applies Lorentz force at opposite direction of the flow, which causes asymmetric distribution of pressure. As a result, pressure in the upper half of the cylinder is higher than the lower half. Finally, velocity and temperature contours along the channel for different Hartmann numbers, volume fraction 3 per cent, Re = 50 and 100 and Gr = 10,000, are presented. Findings The effect of Reynolds number and the influence of magnetic field and pressure drop on convective heat transfer coefficient were studied in different volume fractions of nanoparticles at different Reynolds numbers. Originality/value Effect of MHD on the flow and heat transfer characteristics of Water–Al2O3 nanofluid in a grooved channel with internal heat generation in solid cylinders.

Experimental investigation of the effect of an external magnetic field on the thermal conductivity and viscosity of Fe3O4–glycerol

Thermophysical properties, such as thermal conductivity and viscosity, of magnetic nanofluids (MNFs) can be enhanced by applying external magnetic fields. Such property enhancement can be beneficial for having a non-contact control of heat transfer rates in many applications such as cooling of electronic devices, heating mediator for targeted cancer treatment, drug delivery, and heat transfer medium in energy conversion systems. In this study, a detailed experimental investigation has been carried out to measure the thermal conductivity and viscosity of a magnetic nanofluid under the influence of a uniform external magnetic field. The MNF (i.e., glycerol–Fe3O4) is prepared by dispersing Fe3O4 magnetic nanoparticles in glycerol at different volume fractions of nanoparticles (i.e., φ = 0.5, 1.0, 1.5, 2.0, and 3.0%). The experimental results showed that the viscosity linearly increased with the increase in volume fractions while significantly decreased with the increase in temperature. With respect to the viscosity measurement, the maximum ratio revealed a value of 7.2 for 3.0% volume fraction and 50 °C subjected to 543 [G] magnetic field. Also, a 16.9% thermal conductivity enhancement was achieved when φ = 3.0% at 40 °C under 543 [G] magnetic field. Using the experimental results, a nonlinear model was developed as a function of temperature (T), magnetic field (B), and volume fractions of nanoparticles (φ) to predict the thermal conductivity of glycerol–Fe3O4. The proposed model provided satisfactory performance with an R2 value of 0.961, MSE value of 0.00015, and MAE value of 0.00932.

Experimental investigation on convective heat transfer coefficient of water/ethylene glycol-carbon nanotube nanofluids

ABSTRACTThe objective of the work is to study the enhancement of convective heat transfer of the nanofluid as a function of a different volume fraction of nanoparticles at the different operating temperatures. This work deals with the use of carbon nanotube (CNT) nanofluids with CNT as a nanoparticle and ethylene glycol (EG)/water as a base fluid. In this study, CNT and their thermophysical properties were reviewed and discussed. To investigate the convective heat transfer, an experimental set-up is to be fabricated. The experimental set-up is used to analyse the thermophysical properties of CNT nanofluids.

The effect of using water/CuO nanofluid and L-shaped porous ribs on the performance evaluation criterion of microchannels

The main purpose of this study is numerically investigating the flow and heat transfer of nanofluid flow inside a microchannel with L-shaped porous ribs as well as studying the effect of porous media properties on the performance evaluation criterion (PEC) of the fluid. In the present paper, in addition to the pure water fluid, the effect of using water/CuO nanofluid on the PEC of microchannel was investigated. The flow was simulated in four Reynolds numbers and two different volume fractions of nanoparticles in laminar flow regime. The investigated parameters are the thermal conductivity and the porosity rate of porous medium. The results indicate that with the existence of porous ribs, the nanofluid does not have a significant effect on heat transfer increase. By using porous ribs in flow with Reynolds number of 1200, the heat transfer rate increases up to 42% and in flow with Reynolds number of 100, this rate increases by 25%.

Thermal Conductivity Enhancement by Adding Nanoparticles to Ionic Liquids

Ionanofluids are a very new class of nanofluids having ionic liquids as the base fluid. Thermophysical properties of base ionic liquids (ILs) and nanoparticle enhanced ionic liquids (NEILs) are part of studying a new class of fluids for heat transfer. NEILs are formed by dispersing different volume fractions of nanoparticles in a base ionic liquid. In this article, only the thermal conductivity enhancement was considered for comparison of the different ionanofluids. NEILs show enhanced thermal conductivity compared to the base ILs. Maximum thermal conductivity enhancement was observed by adding 1 % MWCNT to [C4mim][(CF3SO2)2N] ionic liquid. However, if 0.05% MWCNT are added to [(C6)3PC14)][NTf2] no enhancement in thermal conductivity was noticed.

Natural convective heat transfer characteristics of Rayleigh-Benard convection of Al<sub>2</sub>O<sub>3</sub>-water nanofluids

Transient three-dimensional numerical computations are implemented to clarify the natural convective heat transfer characteristics of the Rayleigh-Benard convection of Al2O3-water nanofluids induced in a shallow vertical cylindrical enclosure. The thermophysical properties of nanofluids, assumed to be a single-phase fluid in the numerical computations, are estimated using the experimental correlation equations reported by Khanafer and Vafai (2011). When the average Nusselt numbers of nanofluids are plotted against the Rayleigh number defined by the thermophysical properties of water, computations for four different volume fractions of nanoparticles were below the average Nusselt number curve experimentally reported by Silveston (1958). The diagram also reveals that the increase of nanoparticles in the base fluid delays the generation of Rayleigh-Benard convection. However, the average Nusselt numbers of nanofluids almost agreed with the average Nusselt numbers of Silveston without depending on the volume fraction of nanoparticles when plotted against the Rayleigh number defined by the thermophysical properties of nanofluids. Thus, the natural convection heat transfer rates of Al2O3-water nanofluids can be considered to be similar to the general fluids reported by Silveston as long as experimental thermophysical properties are employed.

Multi-objective optimization of cost and thermal performance of double walled carbon nanotubes/water nanofluids by NSGA-II using response surface method

This study was conducted with the aim of optimizing Double walls carbon nanotubes (DWCNTs)/Water nanofluid from the aspect of cost reduction and improving its thermal performance. Thermal performance factor was obtained for different volume fractions of nanoparticles and Reynolds number based on experimental data. Cost of each sample is also determined based on volume fraction of nanoparticles. Then functions of the thermal performance factors and costs were calculated by response surface method using regression higher than 0.9. Multi-objective optimization method which is effectively capable of achieving optimum answers was utilized. At the end Pareto front and optimized thermal performance factors and the corresponding lowest cost were attained. Furthermore, in order to reach the optimized pattern of lowest cost according to the most desirable thermal performance, the appropriate equation is presented. The results of optimization indicate that the cost was reduced by 38% regarding the earliest iteration.

Simulation of Natural Convection Heat Transfer Enhancement by Nanoparticles in an Open-Enclosure Using Lattice Boltzmann Method

A numerical analysis is performed to investigate the laminar, free convection flow in an Open Enclosure Using Lattice Boltzmann Method (LBM) in the presence of Carbon nanotube and Cu nanoparticles. The problem is studied for different volume fractions of nanoparticles, and aspect ratio of the cavity for various Rayligh numbers. The volume fraction of added nanoparticles to water (as base fluid) is lower than 1% to make dilute suspensions. The study presents a numerical treatment based on LBM to model convection heat transfer of Carbon nanotube based nanofluids. Results show that adding a low value of Carbon nanotube to the base fluid led to significant enhancement of convection rate. Results show that adding nanoparticles to the base fluid enhances the rate of natural convection in a cavity. Make a comparison between Carbon nanotube and Cu-nanoparticles shows that the Carbon nanotube-nano- particle has better performance to enhance convection rate at comparison with Cu- nanoparticles.

Numerical study of turbulent forced convection jet flow of nanofluid in a converging sinusoidal channel

Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluid, as such suspensions are often called, indicate that the suspended nanoparticles remarkably change the transport properties and heat transfer characteristics of the suspension. Bending walls can also improve heat transfer by increasing the total heat transfer from a surface and changing the behavior of the flow. In this paper two-dimensional incompressible nanofluid flow in a confined sinusoidal converging jet in turbulent flow regime is numerically investigated. Results have been shown for the flow structure at different Reynolds numbers for steady asymmetric jet development at various values of the duct-to-jet width ratio (aspect ratio), different amplitudes of surface undulation and different volume fractions of nanoparticles. For considering unsteady treatment of the flow, the streamlines and temperature contours result for the unsteady problem is presented and compared with the steady results. The present computations are in a very good agreement with experimental results in open literature. The results show that by increasing the Reynolds number, aspect ratio, amplitude and volume fraction the average the Nusselt number will increase.

Physicomechanical Characteristics of an Elastomeric Composite Containing Silicon Oxide Nanoparticles with Account of Interface Layer

The results of experimental investigations into the density and the elastic and dissipative properties (elastic modulus, loss modulus, and loss-angle tangent) of an elastomeric nanocomposite (compound of butadienestyrene and butadiene rubbers and silicon oxide nanoparticles) with different volume fractions of filler are presented. It is shown that the density of the interface layer (modified matrix on the contact surface with filler) is lower than the density of matrix, but the elastic modulus of the layer is higher than that of the matrix. A method allowing one to determine the thickness and density of the interface layer is proposed. Analytical relations for calculating the physicomechanical properties of nanocomposites with different volume fractions of nanoparticles are presented.

Mechanical behavior of the alumina-filled silicone rubber under pure shear at finite strain

The mechanical behavior of filler-reinforced rubber was investigated under pure shear at large deformation. Nanocomposites were composed of silicone rubber with different volume fractions of aluminum oxide nanoparticles, ranging from 0% to 5.0%. Thin sheet specimens were manufactured and submitted to monotonic tensile loading. The Digital Image Correlation method was employed to obtain displacement fields and consequently the stress–stretch responses were achieved. The experimentally measured stress–stretch curves were fitted to Yeoh and Lopez-Pamies models in order to estimate material parameters of the neat silicone rubber. Using this information, Mullins–Tobin and Bergstrom–Boyce approaches were employed to evaluate the strain amplification factor of the nanocomposites with different volume fractions of nanoparticles. The results indicate that a significant increase in the stiffness of filled rubber is obtained by small concentrations of nanoparticles. The effect of nanoparticles on mechanical behavior of reinforced rubber can be described using Yeoh and Lopez-Pamies models with Mullins–Tobin and Bergstrom–Boyce approaches. However, the strain amplification factor expression proposed by Bergstrom–Boyce was not suitable to describe the obtained results. In the case, the Guth model was more indicated.

Lattice Boltzmann simulation of natural convection heat transfer of SWCNT-nanofluid in an open enclosure

Abstract The effects of Single Walled Carbon Nanotube and Copper nanoparticles on natural convection heat transfer in an open cavity are investigated numerically. The problem is studied for different volume fractions of nanoparticles (0–1%) and aspect ratio of the cavity (1–4) when Rayleigh number varies from 103 to 105. The volume fraction of added nanoparticles to Water is lower than 1% to make a dilute suspension. Although, results show that adding nanoparticles to the base fluid enhances the heat transfer, make a comparison between SWCNT and Cu-nanoparticles shows that the SWCNT-nanoparticle has better performance to enhance the convection rate. It is found that the aspect ratio of the cavity plays an important role on natural convection. An increase of this parameter leads to heat transfer reduction in the target problem. It is concluded that the Carbon Nanotubes can be applied as a passive way to enhance heat transfer in convection problems.

Effect of Variable Fluid Properties on Natural Convection of Nanofluids in a Cavity with Linearly Varying Wall Temperature

The present study analyzed convective heat transfer and fluid flow characteristics of nanofluid in a two-dimensional square cavity under different combinations of thermophysical models of nanofluids. The right vertical wall temperature is varying linearly with height and the left wall is maintained at low temperature whereas the horizontal walls are adiabatic. Finite volume method is used to solve the governing equations. Two models are considered to calculate the effective thermal conductivity of the nanofluid and four models are considered to calculate the effective viscosity of the nanofluid. Numerical solutions are carried out for different combinations of effective viscosity and effective thermal conductivity models with different volume fractions of nanoparticles and Rayleigh numbers. It is found that the heat transfer rate increases for Models M1 and M3 on increasing the volume fraction of the nanofluid, whereas heat transfer rate decreases for Model M4 on increasing the volume fraction of the nanoparticle. The difference among the effective dynamic viscosity models of nanofluid plays an important role here such that the average Nusselt number demonstrates an increasing or decreasing trend with the concentration of nanoparticle.

Influence of Al2O3 and CuO nanoparticles on the thermal properties of polyester- and epoxy-based nanocomposites

The modification of polymer properties through the addition of nanoparticles has lead to the development of the so-called nanocomposites. The purpose of this study was to investigate the effect of Al2O3 and CuO nanoparticles on the thermo-physical properties of epoxy- and polyester-based nanocomposites. Analysis was carried out for different volume fractions of nanoparticles, ranging from 2.5 to 10 %. The results showed that the glass transition temperature (Tg) varies differently on each matrix and nanoparticles sizes. However, the obtained Tg showed no significant change with nanoparticle concentration. The cross-link density studied by DMA for each nanocomposite shows that Al2O3 fillers are responsible for the decrease in cross-link density, while CuO nanoparticles contribute to improve this property. A significant improvement of thermal stability of epoxy and unsaturated polyester resins containing CuO nanoparticles was observed.

Numerical Analysis of Turbulent Forced Convection of Nanofluid Flow over a Heated Shallow Cavity

This work presents a numerical investigation of turbulent forced convection of a nanofluid over a heated cavity in a horizontal duct. Heat transfers in separated flows are frequently encountered in engineering applications, such as: heat exchangers, axial and centrifugal compressor blades, gas turbines blades, and microelectronic circuit boards. Thus, it is very essential to understand the mechanisms of heat transfer in such regions in order to enhance heat transfer. Different volume fractions of nanoparticles are presented in the base fluid and different types of nanoparticles are used. The objective of this study is to check the effect of nanofluid on heat transfer in such a configuration. Numerical simulations are performed for pure water and four nanofluids (Cu, CuO, Ag, and Al2O3). The results are analyzed through the thermal and dynamical fields with a particular interest to the skin friction coefficient and Nusselt number evolutions. The average Nusselt number increases with the volume fraction of nanoparticles for the whole tested range of Reynolds number. A correlation of average Nusselt number versus Reynolds number and volume fraction of each type of nanoparticles over the cavity wall is proposed in this paper.

Flow and Heat Transfer of Nanoencapsulated Phase Change Material Slurry Past a Unconfined Square Cylinder

Numerical solution is carried out to analyze the effect of nanoencapsulated phase change material (NEPCM) slurry on forced convection heat transfer of steady laminar flow past an isothermal square cylinder. The base fluid is water while the NEPCM particles material is n-octadecane with an average diameter of 100 nm. A parametric study was performed for different volume fraction of nanoparticles ranging from 0% to 30%, two melting temperature ranges, i.e., 10 K and 20 K, and different inlet Reynolds numbers ranging from 15 to 45. The governing equations of flow and energy are solved simultaneously using a finite volume method (FVM) on collocated grid arrangement. It was found that for both NEPCM slurry and pure water, local and average heat transfer coefficients increases with increasing Reynolds number. The results of heat transfer characteristics of slurry flow over the square cylinder showed remarkable enhancement relative to that of the base fluid. The enhancement intensifies for higher particle volume concentrations and higher Reynolds numbers. However, utilizing the slurry can cause higher shear stress on the wall due to higher viscosity of mixture compared to the pure water. The melting temperature range of NEPCM particles has slight effect on heat transfer, although with increasing volume fraction and Reynolds number, lower melting range leads to higher heat transfer coefficient.