Increase In Volume Fraction Of Nanoparticles Research Articles

Heat Source/Sink Effects on a Hybrid Nanofluid-Filled Porous Cavity

Magnetohydrodynamic natural convection flow and heat transfer in a square porous cavity differentially heated and cooled by heat source and sink, respectively, and filled with the –water hybrid nanofluid is studied numerically. The active parts of the left and the right side walls of the cavity are maintained at cooled temperature, and the active parts of the top and bottom walls are maintained at hot temperature. The enclosure’s inactive parts of its side walls are kept insulated. The governing equations in the two-dimensional space are discretized using finite difference methodology. A proper upwinding scheme is employed to obtain stabilized solutions. Using the developed code, a parametric study is undertaken, and the effects of the Rayleigh number, the locations of the active parts of the side walls, and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that the average Nusselt number decreases substantially for hybrid suspension when the location of the heat source changes. It is noted that the velocity decreases in magnitude when Hartmann number increases. The local Nusselt number gets enhanced for the hybrid suspension as the nanoparticle volume fraction increases. It is also shown that, as compared to Cu and , the hybrid suspension has lower magnitude of average Nusselt number.

MHD flow of carbon in micropolar nanofluid with convective heat transfer in the rotating frame

Abstract This article addresses the MHD flow of micropolar carbon-water nanofluid in the presence of rotating frame. Two types of carbon nanotubes (single and multi-walls) are homogeneously dispersed in the base fluid (water). Convective heat transfer phenomenon is also retained in this study. With the help of the similarity transformation, a mathematical model is developed by transforming the partial differential equation into ordinary differential equation. Further it is then solved analytically by using homotopy analysis method HAM. The impact of emerging parameters, skin friction coefficient and Nusselt number are also discussed in detail. It is observed that temperature profile decreases with the increase in porosity parameter and nanoparticle volume fraction while enhances for higher values of Biot number. Further Micro rotation profile increases with the increase in coupling parameter N 1 and Reynolds number R while decreases with increase in Biot number Bi and volume fraction ϕ .

Natural Convection of Water-based Nanofluids in a Square Cavity with Partially Heated of the Bottom Wall

Numerical study of natural convection of water-based nanofluids in a square cavity with partially heated at the bottom wall and filled with nanofluids is carried out using different types of nanoparticles. The remaining wall of this enclosure is kept at cold temperature. The numerical procedure used in this work is based on the Galerkin weighted residual method of finite element formulation.Calculation are performed for Rayleigh numbers in the range 103 -106 and different solid volume fraction of nanoparticles 0 ≤ φ ≤ 0.2. An enhancement in heat transfer rate is observed with the increase of nanoparticles volume fraction for the whole range of Rayleigh numbers. It is observed that the heat transfer enhancement strongly depends on the type of nanofluids.

Radiated flow of chemically reacting nanoliquid with an induced magnetic field across a permeable vertical plate

Impact of induced magnetic field over a flat porous plate by utilizing incompressible water-copper nanoliquid is examined analytically. Flow is supposed to be laminar, steady and two-dimensional. The plate is subjected to a regular free stream velocity as well as suction velocity. Flow formulation is developed by considering Maxwell–Garnetts (MG) and Brinkman models of nanoliquid. Impacts of thermal radiation, viscous dissipation, temperature dependent heat source/sink and first order chemical reaction are also retained. The subjected non-linear problems are non-dimensionalized and analytic solutions are presented via series expansion method. The graphs are plotted to analyze the influence of pertinent parameters on flow, magnetism, heat and mass transfer fields as well as friction factor, current density, Nusselt and Sherwood numbers. It is found that friction factor at the plate is more for larger magnetic Prandtl number. Also the rate of heat transfer decayed with increasing nanoparticles volume fraction and the strength of magnetism.

Slip flow and nonlinear radiative heat transfer of suspended nanoparticles due to a rotating disk in the presence of convective boundary condition

The slip flow and nonlinear radiative heat transfer of suspended nanoparticles due to a rotating disk is analysed in the present work. Two types of nanoparticles namely copper and aluminium oxide and water is treated as base fluid. Suitable similarity transformations are used to reduce the nonlinear partial differential equations to ordinary differential equations. Flow and heat transfer characteristics are computed by numerical technique Runge-Kutta-Fehlberg-fourth and fifth order method. Further, the skin friction coefficient and Nusselt number are presented and examined for pertinent parameters. It is noticed that the higher velocity slip parameter decreases the radial and azimuthal velocities. Also, the rate of heat transfer enhances when the nanoparticle volume fraction increases.

Experimental Investigation of Laminar Convection Heat Transfer of Al2O3-Ethylene Glycol-Water Nanofluid as a Coolant in a Car Radiator

In this experimental study, heat transfer of a coolant nanofluid, obtained by adding alumina nanoparticles to Ethylene Glycol-water (60:40 by mass), in a car radiator has been investigated. For this purpose, an experimental setup has been designed and constructed. Firstly, to investigate the accuracy of the results, the experiments have been done for the base fluid. Then the experiments have been performed for the nanofluid with different nanoparticles volume fractions of 0.003, 0.006, 0.009 and 0.012. To ensure laminar flow regime three coolant flow rates of 9, 11 and 13 lit/min have been tested. The thermophysical properties have been calculated using the recently presented temperature dependent models in the literature. According to the results, both the convective heat transfer coefficient and Nusselt number increase (about 9%) with increasing the coolant flow rate. Also, convective heat transfer coefficient increases with increasing the nanoparticles volume fraction. Although Nusselt number decreases when nanofluid is utilized, it enhances as the nanoparticles volume fraction increases. Based on the experimental results obtained, A new empirical correlation has been developed for average Nusselt number of Al2O3-EG-water nanofluid in developing region of flat tubes of car radiator for laminar flow and its maximum error is 3%.

Three-dimensional computational fluid dynamics modeling of TiO2/R134a nanorefrigerant

In this study, numerical investigations were carried out for R134a based TiO2 nanorefrigerants. Forced laminar flow and heat transfer of nanorefrigerants in a horizontal smooth circular cross-sectioned duct were investigated under steady-state condition. The nanorefrigerants consist of TiO2 nanoparticles suspended in R134a as a base fluid with four particle volume fractions of 0.8, 2.0 and 4.0%. Numerical studies were performed under laminar flow conditions where Reynolds numbers range from 8?102 to 2.2?103. Flow is flowing in the duct with hydrodynamically and thermally developing (simultaneously developing flow) condition. The uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition was applied on the duct wall. Commercial CFD software, Ansys Fluent 14.5, was used to carry out the numerical study. Effect of nanoparticle volume fraction on the average convective heat transfer coefficient and average Darcy friction factor were analyzed. It is obtained in this study that increasing nanoparticle volume fraction of nanorefrigerant increases the convective heat transfer in the duct; however, increasing nanoparticle volume fraction does not influence the pressure drop in the duct. The velocity and temperature distribution in the duct for different Reynolds numbers and nanoparticle volume fractions were presented.

Al2O3/water nano-fluid forced convective flow in a rectangular curved micro-channel: first and second law analysis, single-phase and multi-phase approach

Al2O3/water nano-fluid flow is investigated in a rectangular curved micro-channel using computational fluid dynamics and a comparative study has been conducted between single-phase and multi-phase approaches for modeling of nano-particles addition. The effects of nano-particles volume fraction and Reynolds number on pressure drop, Nusselt number and entropy generation are assessed. Results showed that, increasing nano-particles volume fraction raises Nusselt number, in addition to pressure drop enhancement. Entropy generation due to fluid friction, heat transfer and total entropy generation are also analyzed and the effects of different parameters are investigated. According to the results, nano-particles volume fraction decreases entropy generation due to heat transfer and enhances entropy generation due to fluid friction. It is also noted that nano-particles volume concentration and Reynolds number can alter the dominant source of irreversibility on total irreversibility. Furthermore, Eulerian multi-phase mixture model is compared with single-phase model in curved rectangular micro-channel.

Flow and Heat Transfer of Gold-Blood Nanofluid in a Porous Channel with Moving/Stationary Walls

AbstractThe present study investigates the flow and heat transfer characteristics of blood carrying gold nanoparticles in a porous channel with moving/stationary walls in the presence of thermal radiation. Blood is considered as Newtonian fluid which is the base fluid and gold (Au) as nanoparticles. The governing equations are transformed into system of ordinary differential equations by using similarity transformations. The analytical solutions are obtained for the flow variables by employing homotopy analysis method (HAM). The analytical solutions are compared with the numerical solutions which are obtained by shooting technique along with Runge-Kutta scheme. It was noticed that there is a good agreement between analytical and numerical results. The influence of various parameters on velocity, temperature and heat transfer rate of gold-blood nanofluid has been discussed in detail. The temperature of the nanofluid increases with increasing the nanoparticle volume fraction. The heat transfer rate at the top wall increases with increasing nanoparticle volume fraction while it decreases for a given increase in radiation parameter.

Forced convective heat transfer of nanofluids around a circular bluff body with the effects of slip velocity using a multi-phase mixture model

Forced convective heat transfer around a circular cylinder using nanofluids has been numerically analyzed employing a mixture model based Multi-Phase Modeling (MPM) approach. A hot circular cylinder with a constant wall temperature is exposed to a free stream of Al2O3–H2O nanofluid at ambient temperature. The flow is steady, laminar and two dimensional in the Reynolds number range of 10⩽Re⩽40. The governing equations of flow and energy transfer along with the respective boundary conditions are numerically solved using a Finite Volume Method (FVM) based on SIMPLE algorithm. The prime aim of this work is to highlight the effects of slip velocity, volume concentration and diameter of nanoparticles on heat transfer characteristics of nanofluids. Results indicate that heat transfer increases with increase in nanoparticle volume fraction. The highest mean Nusselt number is observed at ϕ=5% at any Reynolds number. It is also noted that, nanofluids with smaller nanoparticles result in higher heat transfer rates. Particular attention has been paid to the variation of heat transfer characteristics when the modeling approach is switched from Single-Phase Modeling (SPM) to mixture model based MPM. It is revealed that higher heat transfer rates are observed in MPM which considers the effects of slip velocity.

How the dispersion of magnesium oxide nanoparticles effects on the viscosity of water-ethylene glycol mixture: Experimental evaluation and correlation development

In this paper, the effect of dispersion of magnesium oxide nanoparticles on viscosity of a mixture of water and ethylene glycol (50–50% vol.) was examined experimentally. Experiments were performed for various nanofluid samples at different temperatures and shear rates. Measurements revealed that the nanofluid samples with volume fractions of less than 1.5% had Newtonian behavior, while the sample with volume fraction of 3% showed non-Newtonian behavior. Results showed that the viscosity of nanofluids enhanced with increasing nanoparticles volume fraction and decreasing temperature. Results of sensitivity analysis revealed that the viscosity sensitivity of nanofluid samples to temperature at higher volume fractions is more than that of at lower volume fractions. Finally, because of the inability of the existing model to predict the viscosity of MgO/EG-water nanofluid, an experimental correlation has been proposed for predicting the viscosity of the nanofluid.

Mixed convection in a partially heated triangular cavity filled with nanofluid having a partially flexible wall and internal heat generation

Abstract Numerical study of mixed convection in a partially heated nanofluid-filled lid driven cavity with internal heat generation and having a partial flexible wall was performed. The bottom wall of the triangular enclosure is moving with constant speed and left vertical wall is partially heated. The inclined wall of the cavity is cooled and partially flexible. The governing equations are solved with Galerkin weighted residual finite element method. The effects of Richardson number (between 0.05 and 50), internal Rayleigh number (between 10 4 and 10 8 ), size and elastic modulus of the partial flexible wall and nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer were numerically investigated. It was observed that the local and averaged heat transfer reduce as the value of the Richardson number and internal Rayleigh number increase. As the value of the elastic modulus of the inclined wall and nanoparticle volume fraction increase, local and average heat transfer enhance. The discrepancy between the averaged Nusselt number increase for different sizes for the lower values of elastic modulus of the flexible wall. When heat transfer process is effective adding nanoparticles to the base fluid is advantageous.

Investigation of Hall current and slip conditions on peristaltic transport of Cu-water nanofluid in a rotating medium

Main objective of present study is to analyze the effect of rotation on peristaltic transport of copper-water nanofluid. Two phase nanofluid is employed. The fluid fills the porous space. The channel walls are taken flexible. Hall current and viscous dissipation effects are also given consideration in the modeling. Analysis also studies the slip conditions in presence of heat generation/absorption. Resulting coupled system of equations is simplified by employing lubrication approach. Exact solutions are presented for the stream function whereas energy equation is solved numerically. Impact of sundry parameters on flow quantities are discussed and displayed via graphs. It is concluded that both axial (u) and secondary (v) velocities are reduced for increasing nanoparticle volume fraction (ϕ). Hartman number (M) and Hall parameter (m) have opposite effects on the velocity. Temperature (θ) enhances for increasing Hartman number (M).

A Numerical Analysis of Fluid Flow and Heat Transfer Characteristics of ZnO-Ethylene Glycol Nanofluid in Rectangular Microchannels

The fluid flow and heat transfer characteristics of ZnO-Ethylene glycol (EG) nanofluid through rectangular microchannels having different aspect ratios (α is 1 to 2) are numerically investigated. The different nanoparticle volume percentages (φ is 1 % to 4 %) of ZnO-EG nanofluid are used. The flow is considered under single-phase, three-dimensional, steady-state, incompressible, thermally developing, laminar flow conditions. As a result, the microchannel with an aspect ratio value of 1 has the highest convection heat transfer coefficient and the lowest pressure drop. It is also observed that the convection heat transfer coefficient and pressure drop increases with an increase in nanoparticle volume fraction value of nanofluid. However, the Nusselt number decreases with increasing nanoparticle volume fraction, while the Darcy friction factor is not affected.

Numerical investigation of combined buoyancy-thermocapillary convection and entropy generation in 3D cavity filled with Al2O3 nanofluid

Heat transfer, fluid flow and entropy generation due to combined buoyancy and thermocapillary forces in a 3D differentially heated enclosure containing Al2O3 nanofluid are carried out for different Marangoni numbers and different nanoparticles concentrations. The vector potential-vorticity formalism and the finite volume method are used respectively to formulate and to solve the governing equations and calculations were performed for Marangoni number from −103 to 103, volume fraction of nanoparticles from 0 to 0.2 and for a fixed Rayleigh number at 105. An intensification of the flow and an increase in heat transfer and of total entropy generation occur with the increase in nanoparticles volume fraction for all Marangoni numbers.

Three dimensional numerical investigations on the heat transfer enhancement in a triangular facing step channels using nanofluid

In this paper, laminar flow for the distilled and SiO2-water nanofluid flow and heat transfer were numerically investigated in three-dimensional triangular facing-step channel. The nanoparticle volume fraction and Reynolds number considered are in the range of 0-1% and 100-1500, respectively. Numerical solutions are obtained by using finite difference method to solve the governing equations. The effects of the volume fraction of nanoparticle, triangular facing-step channel amplitude height, wavelength and Reynolds number on local skin-friction coefficient, average Nusselt number and enhancement of heat transfer are presented and discussed. The results show that the Nusselt number and friction coefficient increases as the amplitude height of triangle channel increases. As the nanoparticle volume fraction increases, the Nusselt number is also found to be significantly increased, accompanied by only a slight increase in the friction coefficient. In addition, it is found that the heat transfer enhancement mainly depends on the amplitude height of the triangle wall, nanoparticle volume fraction and Reynolds number rather than the wavelength.

Experimental investigation of thermal performance for direct absorption solar parabolic trough collector (DASPTC) based on binary nanofluids

Nanofluids can be utilized to capture and distribute effectively solar radiation due to the capability of their nanoparticles in the liquid medium to scatter and absorb solar radiation. Hence, nanofluid-based solar collectors have the potential to harness solar radiant energy. Proper nanofluids can be selected for solar applications based on their potential optical properties. Binary nanofluids as a new class of nanofluids comprising a base fluid and two different nanoparticles may exhibit a behavior different from any of their components. The behavior of such nanofluids has not yet been extensively investigated. The present experimental study was, therefore, designed and implemented to investigate the absorption and thermal conductivity of binary nanofluids and to evaluate the factors involved in their optimal stability. For this purpose, two dissimilar nanoparticles, i.e. CuO (with high absorption properties) and γ-Al2O3 (with high scattering properties) were chosen to prepare a binary nanofluid. Results showed that the thermal conductivity and aggregation of the prepared nanofluid were highest and lowest, respectively, under optimal stability conditions. As another main goal of this study, the effect of the binary nanofluid on the thermal efficiency of direct absorption solar parabolic trough collectors (DASPTCs) was evaluated. Results showed that solar irradiance is absorbed and converted into a significant amount of sensible heat along the length of the receiver pipe. Experiments with the DASTPC collector also revealed that the thermal efficiency of the system could be enhanced by increasing nanoparticle volume fraction and nanofluid flow rate.

A Study on Hydromagnetic Pulsating Flow of a Nanofluid in a Porous Channel With Thermal Radiation

AbstractThe present study investigates the hydromagnetic pulsating nanofluid flow in a porous channel with thermal radiation. In this work, we considered water as the base fluid and silver (Ag), copper (Cu), alumina (Al2O3) and titanium dioxide (TiO2) as nanoparticles. The Maxwell-Garnetts and Brinkman models are used to evaluate the effective thermal conductivity and viscosity of the nanofluid. The governing equations are solved analytically and the influence of various parameters on velocity, temperature and heat transfer rate has been discussed through graphical results. From the results, it is found that the rate of heat transfer enhances with an increase of nanoparticle volume fraction. Further, the heat transfer rate is higher for silver nanoparticles as compared with copper, alumina and titanium dioxide.

Investigating the collector efficiency of silver nanofluids based direct absorption solar collectors

A one-dimensional transient heat transfer analysis was carried out to analyze the effects of the Nanoparticle (NP) volume fraction, collector height, irradiation time, solar flux, and NP material on the collector efficiency. The numerical results were compared with the experimental results obtained by silver nanofluids to validate the model, and good agreement was obtained. The numerical results show that the collector efficiency increases as the collector height and NP volume fraction increase and then reaches a maximum value. An optimum collector height (∼10mm) and particle concentration (∼0.03%) achieving a collector efficiency of 90% of the maximum efficiency can be obtained under the conditions used in the simulation. However, the collector efficiency decreases as the irradiation time increases owing to the increased heat loss. A high solar flux is desirable to maintain a high efficiency over a wide temperature range, which is beneficial for subsequent energy utilization. The modeling results also show silver and gold nanofluids obtain higher photothermal conversion efficiencies than the titanium dioxide nanofluid because their absorption spectra are similar to the solar radiation spectrum.

Natural convection investigation in square cavity filled with nanofluid using dispersion model

A cooling achieved with compact and efficient device is one of the major challenges encountered in the promising technique of fuel cell stacks. The safe and reliable use of such a system is highly dependent on the efficiency of the assured heat transfer and consequently on the quality of the coolant used. To test the possible improvement of the coolant performances, laminar natural convection in square cavity filled with copper-water nanofluid is numerically carried out taking into account the thermal dispersion effect on the heat transfer intensity. The finite element method is used to solve the governing equations. The hydrodynamic structure of the flow and its thermal behavior are studied for a wide range of Rayleigh numbers. The obtained results showed an enhancement of heat transfer with an increase in nanoparticle volume fraction for all examined Rayleigh numbers. However, it is found that an increase in nanoparticle diameter enhances heat transfer only when thermal dispersion is significant. Correlation with 99.94% confidence coefficient is proposed to quantify the heat transfer intensity according to the Rayleigh number and particle diameter and concentration.