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4 pages, 154 KiB

Open AccessEditorial

Special Issue on Nanofluids and Their Applications

by Guan Heng Yeoh and Sherman Cheung

Appl. Sci. 2019, 9(7), 1476; https://doi.org/10.3390/app9071476 - 9 Apr 2019

Viewed by 2241

Abstract

Nanofluids can be considered as engineered colloidal suspensions of nanometer-sized particles in a base fluid of water, ethylene glycol, or oil [...] Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

Research

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25 pages, 10398 KiB

Open AccessArticle

Magnetic Field Effect on the Double Diffusive Natural Convection in Three-Dimensional Cavity Filled with Micropolar Nanofluid

by Awatef Abidi, Zehba Raizah and Jamel Madiouli

Appl. Sci. 2018, 8(12), 2342; https://doi.org/10.3390/app8122342 - 22 Nov 2018

Cited by 14 | Viewed by 3318

Abstract

This article presents a three-dimensional numerical investigation of heat and mass transfers and fluid flow in a cavity filled with an Al₂O₃/water micropolar fluid under uniform magnetic field. To solve the governing non-dimensional equations, Finite Volume Method (FVM) based [...] Read more.

This article presents a three-dimensional numerical investigation of heat and mass transfers and fluid flow in a cavity filled with an Al₂O₃/water micropolar fluid under uniform magnetic field. To solve the governing non-dimensional equations, Finite Volume Method (FVM) based on 3-D vorticity-vector potential formulation has been employed. The effects of various parameters such as buoyancy ratio (−2 ≤ N ≤ 0), Rayleigh number (10³ ≤ Ra ≤ 10⁵), Hartmann number (0≤ Ha≤ 60), nanoparticles volume fraction (0 ≤ φ ≤ 0.06) and micropolar material parameter (0≤ K≤ 5) on flow structure and on heat and mass transfers are presented. The results illustrate that for the micropolar nanofluid model, both heat and mass transfer rates and three-dimensional character of the flow are smaller when compared with the pure nanofluid model. It is also observed that increase and decrease in heat and mass transfer rates is experienced due to increase in Rayleigh number and Hartmann number, respectively. It is also noted that increase in vortex viscosity parameter reduces the average heat and mass transfer rates and is more evident when the magnetic field is imposed. Combined effects of magnetic field and nanoparticles volume fraction on heat and mass transfers are also explored. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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23 pages, 1701 KiB

Open AccessArticle

Ethylene- and Propylene-Glycol Based Nanofluids: A Litterature Review on Their Thermophysical Properties and Thermal Performances

by Ghofrane Sekrani and Sébastien Poncet

Appl. Sci. 2018, 8(11), 2311; https://doi.org/10.3390/app8112311 - 20 Nov 2018

Cited by 52 | Viewed by 8444

Abstract

Nanofluids are considered a promising way to improve the heat transfer capability of base fluids. Water is the most commonly-used heat transfer fluid. However, in refrigeration systems, it may be necessary to mix water with either ethylene- or propylene-glycol to lower its freezing [...] Read more.

Nanofluids are considered a promising way to improve the heat transfer capability of base fluids. Water is the most commonly-used heat transfer fluid. However, in refrigeration systems, it may be necessary to mix water with either ethylene- or propylene-glycol to lower its freezing point and prevent from ice formation. In the same way, for car radiators or industrial heat exchangers, the boiling point of water can be pushed up by mixing it with glycol-based fluids. The increasing awareness of energy saving and industrial energy efficiency improvement results in the growing interest in ethylene- or propylene-glycol-based nanofluids for applications in various thermal systems. The present paper proposes an extensive review of the most recent and relevant experimental and numerical works on the thermophysical properties and performances of ethylene- or propylene-glycol-based nanofluids. Research perspectives are also provided with the long-term objective that these nanofluids be more widely considered in real industrial applications. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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18 pages, 3578 KiB

Open AccessArticle

Unsteady Stagnation-Point Flow and Heat Transfer Over a Permeable Exponential Stretching/Shrinking Sheet in Nanofluid with Slip Velocity Effect: A Stability Analysis

by Nor Fadhilah Dzulkifli, Norfifah Bachok, Nor Azizah Yacob, Norihan Md Arifin and Haliza Rosali

Appl. Sci. 2018, 8(11), 2172; https://doi.org/10.3390/app8112172 - 6 Nov 2018

Cited by 36 | Viewed by 5648

Abstract

A model of unsteady stagnation-point flow and heat transfer over a permeable exponential stretching/shrinking sheet with the presence of velocity slip is considered in this paper. The nanofluid model proposed by Tiwari and Das is applied where water with Prandtl number 6.2 has [...] Read more.

A model of unsteady stagnation-point flow and heat transfer over a permeable exponential stretching/shrinking sheet with the presence of velocity slip is considered in this paper. The nanofluid model proposed by Tiwari and Das is applied where water with Prandtl number 6.2 has been chosen as the base fluid, while three different nanoparticles are taken into consideration, namely Copper, Alumina, and Titania. The ordinary differential equations are solved using boundary value problem with fourth order accuracy (bvp4c) program in Matlab to find the numerical solutions of the skin friction and heat transfer coefficients for different parameters such as stretching/shrinking, velocity slip, nanoparticle volume fraction, suction/injection, and also different nanoparticles, for which the obtained results (dual solutions) are presented graphically. The velocity and temperature profiles are presented to show that the far field boundary conditions are asymptotically fulfilled, and validate the findings of dual solutions as displayed in the variations of the skin friction and heat transfer coefficients. The last part is to perform the stability analysis to determine a stable and physically-realizable solution. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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18 pages, 15142 KiB

Open AccessArticle

Thermophysical Analysis of Water Based (Cu–Al₂O₃) Hybrid Nanofluid in an Asymmetric Channel with Dilating/Squeezing Walls Considering Different Shapes of Nanoparticles

by Fitnat Saba, Naveed Ahmed, Umar Khan, Asif Waheed, Muhammad Rafiq and Syed Tauseef Mohyud-Din

Appl. Sci. 2018, 8(9), 1549; https://doi.org/10.3390/app8091549 - 4 Sep 2018

Cited by 70 | Viewed by 4142

Abstract

An innovative concept of water-based Cu–Al₂O₃ hybrid nanofluid has been employed to investigate the behavior of flow and heat transfer inside a rectangular channel whose permeable walls experiences dilation or contraction in height. The transformed set of ordinary differential equations [...] Read more.

An innovative concept of water-based Cu–Al₂O₃ hybrid nanofluid has been employed to investigate the behavior of flow and heat transfer inside a rectangular channel whose permeable walls experiences dilation or contraction in height. The transformed set of ordinary differential equations is then solved by a well-known Runge–Kutta–Fehlberg algorithm. The analysis also includes three different shapes of copper nanocomposites, namely, platelet, cylinder and brick- shaped. The impact of various embedded parameters on the flow and heat transfer distributions have been demonstrated through the graphs. All the flow properties, temperature profile and rate of heat transfer at the walls are greatly influenced by the presence of copper nanoparticles. Furthermore, it was observed that the platelet shaped nanocomposites provide a better heat transfer ability as compared to the other shapes of nanoparticles. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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13 pages, 4196 KiB

Open AccessArticle

Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage

by Hyun Jung Kim and Byeongnam Jo

Appl. Sci. 2018, 8(8), 1305; https://doi.org/10.3390/app8081305 - 5 Aug 2018

Cited by 31 | Viewed by 4867

Abstract

An anomalous increase of the specific heat was experimentally observed in molten salt nanofluids using a differential scanning calorimeter. Binary carbonate molten salt mixtures were used as a base fluid, and the base salts were doped with graphite nanoparticles. Specific heat measurements of [...] Read more.

An anomalous increase of the specific heat was experimentally observed in molten salt nanofluids using a differential scanning calorimeter. Binary carbonate molten salt mixtures were used as a base fluid, and the base salts were doped with graphite nanoparticles. Specific heat measurements of the nanofluids were performed to examine the effects of the composition of two salts consisting of the base fluid. In addition, the effect of the nanoparticle concentration was investigated as the concentration of the graphite nanoparticles was varied from 0.025 to 1.0 wt %. Moreover, the dispersion homogeneity of the nanoparticles was explored by increasing amount of surfactant in the synthesis process of the molten salt nanofluids. The results showed that the specific heat of the nanofluid was enhanced by more than 30% in the liquid phase and by more than 36% in the solid phase at a nanoparticle concentration of 1 wt %. It was also observed that the concentration and the dispersion homogeneity of nanoparticles favorably affected the specific heat enhancement of the molten salt nanofluids. The dispersion status of graphite nanoparticles into the salt mixtures was visualized via scanning electron microscopy. The experimental results were explained according to the nanoparticle-induced compressed liquid layer structure of the molten salts. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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16 pages, 2691 KiB

Open AccessFeature PaperArticle

The Effect of Gold Nanorods Clustering on Near-Infrared Radiation Absorption

by Xi Gu, Victoria Timchenko, Guan Heng Yeoh, Leonid Dombrovsky and Robert Taylor

Appl. Sci. 2018, 8(7), 1132; https://doi.org/10.3390/app8071132 - 12 Jul 2018

Cited by 25 | Viewed by 6511

Abstract

In this paper, the plasmonic resonant absorption of gold nanorods (GNRs) and GNR solutions was studied both numerically and experimentally. The heat generation in clustered GNR solutions with various concentrations was measured by exposing them to Near Infrared (NIR) light in experiment. Correspondingly, [...] Read more.

In this paper, the plasmonic resonant absorption of gold nanorods (GNRs) and GNR solutions was studied both numerically and experimentally. The heat generation in clustered GNR solutions with various concentrations was measured by exposing them to Near Infrared (NIR) light in experiment. Correspondingly, calculations based on the discrete-dipole approximation (DDA) revealed the same relationship between the maximum absorption efficiency and the nanorod orientation for the incident radiation. Additionally, both the plasmonic wavelength and the maximum absorption efficiency of a single nanorod were found to increase linearly with increasing aspect ratio (for a fixed nanorod volume). The wavelength of the surface plasmonic resonance (SPR) was found to change when the gold nanorods were closely spaced. Specifically, both a shift and a broadening of the resonance peak were attained when the distance between the nanorods was set to about 50 nm or less. The absorbance spectra of suspended nanorods at various volume fractions also showed that the plasmonic wavelength of the nanorods solution was at 780 ± 10 nm, which was in good agreement with the computational predictions for coupled side-by-side nanorods. When heated by NIR light, the rate of increase for both the temperature of solution and the absorbed light diminished when the volume fraction of suspended nanorods reached a value of

1.24 \times 10^{- 6}

. This matches with expectations for a partially clustered suspension of nanorods in water. Overall, this study reveals that particle clustering should be considered to accurately gauge the heat generation of the GNR hyperthermia treatments. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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22 pages, 8730 KiB

Open AccessArticle

Three-Dimensional Magnetohydrodynamic Mixed Convection Flow of Nanofluids over a Nonlinearly Permeable Stretching/Shrinking Sheet with Velocity and Thermal Slip

by Anuar Jamaludin, Roslinda Nazar and Ioan Pop

Appl. Sci. 2018, 8(7), 1128; https://doi.org/10.3390/app8071128 - 12 Jul 2018

Cited by 27 | Viewed by 3759

Abstract

In this paper, the steady three-dimensional magnetohydrodynamic (MHD) mixed convection flow of nanofluids over a permeable vertical stretching/shrinking sheet with slip conditions is investigated in a numerical manner. As such, two types of nanofluids, Cu-water and Ag-water, had been considered. A similarity transformation [...] Read more.

In this paper, the steady three-dimensional magnetohydrodynamic (MHD) mixed convection flow of nanofluids over a permeable vertical stretching/shrinking sheet with slip conditions is investigated in a numerical manner. As such, two types of nanofluids, Cu-water and Ag-water, had been considered. A similarity transformation was employed to reduce the governing equations to ordinary differential equations, which were then solved numerically using the MATLAB (Matlab R2015a, MathWorks, Natick, MA, USA, 1984) programme bvp4c. The numerical solutions derived from the ordinary differential equations subjected to the associated boundary conditions, were obtained to represent the values of the mixed convection parameter. Dual (upper and lower branch) solutions were discovered in the opposing flow region of the mixed convection parameter. A stability analysis was carried out to prove that the upper branch solution was indeed stable, while the lower branch solution was unstable. The significant effects of the governing parameters on the reduced skin friction coefficients, the reduced local Nusselt number, as well as the velocity and temperature profiles, were presented graphically and discussed in detail. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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18 pages, 4767 KiB

Open AccessArticle

Effect of Silica Nanoparticles on Fluid/Rock Interactions during Low Salinity Water Flooding of Chalk Reservoirs

by Rockey Abhishek, Aly A. Hamouda and Amr Ayoub

Appl. Sci. 2018, 8(7), 1093; https://doi.org/10.3390/app8071093 - 5 Jul 2018

Cited by 17 | Viewed by 4283

Abstract

The main objective of this work is to address the adsorption of Silica nanoparticles (NPs) dispersed in different brines on chalk surfaces and their effect on fluid/rock interaction. Isothermal static and dynamic adsorption on chalk are addressed here. Isothermal static adsorption showed increased [...] Read more.

The main objective of this work is to address the adsorption of Silica nanoparticles (NPs) dispersed in different brines on chalk surfaces and their effect on fluid/rock interaction. Isothermal static and dynamic adsorption on chalk are addressed here. Isothermal static adsorption showed increased adsorption of NPs at higher salinity. The tests were performed to cover wide range of injection scenarios with synthetic seawater (SSW) and low salinity water (LSW). The selected LSW composition here is based on 1:10 diluted SSW, which has shown to have superior performance compared to other ion compositions. The dynamic adsorption tests of NPs showed reduction of calcite dissolution of about 30% compared to LSW alone. That is, silica nanofluid hinders calcite dissolution i.e., has less effect on chalk matrix integrity which is a major concern in chalk reservoir, if low salinity is employed for enhanced oil recovery. Both scanning electron microscope images and pressure drop across the core during nanofluid injection indicated no throat blockage. Based on ion tracking and the monitored pH, the mechanism(s) for NP adsorption/desorption are suggested. The results from this study suggests a synergy wherein adding relatively small amount of silica NPs can improve the performance of low salinity floods. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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15 pages, 3695 KiB

Open AccessArticle

Measurement and Quantification of Effective Slip Length at Solid–Liquid Interface of Roughness-Induced Surfaces with Oleophobicity

by Yifan Li, Yunlu Pan and Xuezeng Zhao

Appl. Sci. 2018, 8(6), 931; https://doi.org/10.3390/app8060931 - 5 Jun 2018

Cited by 10 | Viewed by 4210

Abstract

Boundary conditions of the liquid–solid interface of micro/nano fluid flow are of great interest, as slippage is linked with decreased drag. However, previous studies have seldom included a systematic analysis of the effect of roughness on the measurement and quantification of slip length. [...] Read more.

Boundary conditions of the liquid–solid interface of micro/nano fluid flow are of great interest, as slippage is linked with decreased drag. However, previous studies have seldom included a systematic analysis of the effect of roughness on the measurement and quantification of slip length. For the measurement of slip length using atomic force microscopy (AFM), which is believed to be the most accurate method, a theoretical description of the drainage of thin liquid films between sphere and surface, with realistic roughness, is yet to be published. This study focuses on the measurement and quantification of slip length on rough surfaces immersed in liquids, based on AFM and laser confocal scanning microscopy. A reformulation of the boundary condition is presented, taking into account the effect of surface roughness. The correction to the effective slip length is analyzed, then surfaces with various degrees of spacing roughness Rsm were fabricated. Quantitative analysis of the effective slip length is presented. Results show that the corrected effective slip length remains constant with increased spacing roughness Rsm of surfaces. The results are discussed for the coagulation process of colloids and measurement of slip lengths on roughness-induced surfaces with AFM. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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16 pages, 1095 KiB

Open AccessArticle

Stability Analysis of Mixed Convection Flow towards a Moving Thin Needle in Nanofluid

by Siti Nur Alwani Salleh, Norfifah Bachok, Norihan Md Arifin, Fadzilah Md Ali and Ioan Pop

Appl. Sci. 2018, 8(6), 842; https://doi.org/10.3390/app8060842 - 23 May 2018

Cited by 39 | Viewed by 3941

Abstract

The problem of steady laminar mixed convection flow and heat transfer past a moving vertical thin needle in nanofluid for both assisting and opposing cases is analyzed in this paper. Three types of nanoparticles including copper, titania and alumina are taken into consideration. [...] Read more.

The problem of steady laminar mixed convection flow and heat transfer past a moving vertical thin needle in nanofluid for both assisting and opposing cases is analyzed in this paper. Three types of nanoparticles including copper, titania and alumina are taken into consideration. The nonlinear ordinary differential equations for momentum and energy have been transformed by adopting the similarity transformation in linear form. The problem is solved numerically using an implemented package called bvp4c in MATLAB software. The numerical computations are carried out for various parameters of interest, which consists of the velocity ratio parameter, mixed convection parameter, nanoparticle volume fraction parameter and the needle size. A stability analysis of the solution is performed showing that the upper branch solution is stable, while the lower branch solution is unstable. Validation of the present work is done by comparing the current results with those available in the existing literature and found to be in excellent agreement. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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17 pages, 6824 KiB

Open AccessArticle

MHD Steady/Unsteady Porous Boundary Layer of Cu–Water Nanofluid with Micropolar Effect over a Permeable Surface

by Kamal Raslan, Selim Mohamadain, Mohamed Abdel-wahed and Elsayed M. Abedel-aal

Appl. Sci. 2018, 8(5), 736; https://doi.org/10.3390/app8050736 - 7 May 2018

Cited by 16 | Viewed by 3417

Abstract

This work provides a mathematical model for the cooling process of a moving surface, in the presence of a uniform external magnetic field and thermal radiation, through a porous medium by using a weak concentration micropolar nanofluid. The model—based on the conservation equations [...] Read more.

This work provides a mathematical model for the cooling process of a moving surface, in the presence of a uniform external magnetic field and thermal radiation, through a porous medium by using a weak concentration micropolar nanofluid. The model—based on the conservation equations of the unsteady case in the momentum and thermal boundary layer—takes into consideration the effect of the suction process. The conservation equations were transformed into ordinary differential equations using similar transformation techniques. The equations were solved numerically for the general case and analytically for the steady case. The rate of heat transfer, couple shear stress, and surface shear stress are deduced. We discuss the impact of these physical characteristics on the mechanical properties of the surface that will be cooled. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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13 pages, 4401 KiB

Open AccessFeature PaperArticle

Stability Analysis of Stagnation-Point Flow in a Nanofluid over a Stretching/Shrinking Sheet with Second-Order Slip, Soret and Dufour Effects: A Revised Model

by Najwa Najib, Norfifah Bachok, Norihan Md Arifin and Fadzilah Md Ali

Appl. Sci. 2018, 8(4), 642; https://doi.org/10.3390/app8040642 - 20 Apr 2018

Cited by 32 | Viewed by 5224

Abstract

The mathematical model of the two-dimensional steady stagnation-point flow over a stretching or shrinking sheet of nanofluid in the presence of the Soret and Dufour effects and of second-order slip at the boundary was considered in this paper. The partial differential equations were [...] Read more.

The mathematical model of the two-dimensional steady stagnation-point flow over a stretching or shrinking sheet of nanofluid in the presence of the Soret and Dufour effects and of second-order slip at the boundary was considered in this paper. The partial differential equations were transformed into the ordinary differential equations by applying a suitable similarity transformation. The numerical results were obtained by using bvp4c codes in Matlab. The skin friction coefficient, heat transfer coefficient, mass transfer coefficient, as well as the velocity, temperature, and concentration profiles were presented graphically for different values of slip parameters, Soret effect, Dufour effect, Brownian motion parameter, and thermophoresis parameter. A dual solution was obtained in this present paper. The presence of the slip parameters (first- and second-order slip parameters) was found to expand the range of solutions. However, the presence of the slip parameters led to a decrease in the skin friction coefficient, whereas the heat transfer coefficient increased. Besides that, a larger Soret effect (smallest Dufour effect) led to the decrement of the heat transfer coefficient. The effects of the Brownian motion and thermophoresis parameters on the heat transfer coefficient were also studied in this paper. A stability analysis was performed in this paper to verify the stability of the solutions obtained. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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9 pages, 21764 KiB

Open AccessArticle

Effects of Nanoparticle Materials on Prebreakdown and Breakdown Properties of Transformer Oil

by Yuzhen Lv, Yang Ge, Lei Wang, Zhen Sun, You Zhou, Meng Huang, Chengrong Li, Jinsha Yuan and Bo Qi

Appl. Sci. 2018, 8(4), 601; https://doi.org/10.3390/app8040601 - 11 Apr 2018

Cited by 11 | Viewed by 4755

Abstract

In order to reveal the effects of nanoparticle materials on prebreakdown and breakdown properties of transformer oil, three types of nanoparticle materials, including conductive Fe₃O₄, semiconductive TiO₂ and insulating Al₂O₃ nanoparticles, were prepared with the [...] Read more.

In order to reveal the effects of nanoparticle materials on prebreakdown and breakdown properties of transformer oil, three types of nanoparticle materials, including conductive Fe₃O₄, semiconductive TiO₂ and insulating Al₂O₃ nanoparticles, were prepared with the same size and surface modification. An experimental study on the breakdown strength and prebreakdown streamer propagation characteristics were investigated for transformer oil and three types of nanofluids under positive lightning impulse voltage. The results indicate that the type of nanoparticle materials has a notable impact on breakdown strength and streamer propagation characteristics of transformer oil. Breakdown voltages of nanofluids are markedly increased by 41.3% and 29.8% respectively by the presence of Fe₃O₄ and TiO₂ nanoparticles. Whereas a slight increase of only 7.4% is observed for Al₂O₃ nanofluid. Moreover, main discharge channels with thicker and denser branches are formed and the streamer propagation velocities are greatly lowered both in Fe₃O₄ and TiO₂ nanofluids, while no obvious change appears in the propagation process of streamers in Al₂O₃ nanofluid in comparison with that in pure oil. The test results of trap characteristics reveal that the densities of shallow traps both in Fe₃O₄ and TiO₂ nanofluids are much higher than that in Al₂O₃ nanofluid and pure oil, greatly reducing the distortion of the electric field. Thus, the propagations of positive streamers in the nanofluids are significantly suppressed by Fe₃O₄ and TiO₂ nanoparticles, leading to the improvements of breakdown strength. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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13 pages, 2040 KiB

Open AccessArticle

A Stability Analysis on Mixed Convection Boundary Layer Flow along a Permeable Vertical Cylinder in a Porous Medium Filled with a Nanofluid and Thermal Radiation

by Shahirah Abu Bakar, Norihan Md Arifin, Fadzilah Md Ali, Norfifah Bachok, Roslinda Nazar and Ioan Pop

Appl. Sci. 2018, 8(4), 483; https://doi.org/10.3390/app8040483 - 23 Mar 2018

Cited by 33 | Viewed by 4351

Abstract

A study on mixed convection boundary layer flow with thermal radiation and nanofluid over a permeable vertical cylinder lodged in a porous medium is performed in this current research by considering groupings of a variety nanoparticles, consisting of copper (Cu), aluminium (Al₂ [...] Read more.

A study on mixed convection boundary layer flow with thermal radiation and nanofluid over a permeable vertical cylinder lodged in a porous medium is performed in this current research by considering groupings of a variety nanoparticles, consisting of copper (Cu), aluminium (Al₂O₃) and titanium (TiO₂). By using a method of similarity transformation, a governing set of ordinary differential equations has been reduced from the governing system of nonlinear partial differential equations, which are the values of selected parameters such as mixed convection parameter

λ

, nanoparticle volume fraction

φ

, radiation parameter Rd, suction parameter S, and curvature parameter

ξ

are solved numerically. From the numerical results, we observed that the involving of certain parameters ranges lead to the two different branches of solutions. We then performed a stability analysis by a bvp4c function (boundary value problem with fourth-order accuracy) to determine the most stable solution between these dual branches and the respective solutions. The features have been discussed in detail. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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18 pages, 2896 KiB

Open AccessArticle

Mathematical Models of Electro-Magnetohydrodynamic Multiphase Flows Synthesis with Nano-Sized Hafnium Particles

by Farooq Hussain, Rahmat Ellahi and Ahmad Zeeshan

Appl. Sci. 2018, 8(2), 275; https://doi.org/10.3390/app8020275 - 12 Feb 2018

Cited by 77 | Viewed by 4556

Abstract

The multiphase fluid flow under the influence of electro-magnetohydrodynamics (EHD) is investigated in this study. The base fluid contains hafnium particles. Two illustrative models namely fluid phase and particulate phase are considered for three different geometries having great importance in both industrial and [...] Read more.

The multiphase fluid flow under the influence of electro-magnetohydrodynamics (EHD) is investigated in this study. The base fluid contains hafnium particles. Two illustrative models namely fluid phase and particulate phase are considered for three different geometries having great importance in both industrial and mechanical usage. The impact of pertinent parameters from different aspects is illustrated graphically with requisite discussion keeping in view their physical aspects. The stream lines are also erected to highlight their physical importance regarding the flow patterns. In addition, the paper is terminated by making a comparison with the existing literature as a limiting case of considered problem to confirm the validations of achieved results and hence found in excellent agreement. This model can be used to design and engineer for nozzle or diffuser type of injectors in the latest models of automobiles to improve their performance and reduce the consumption of fuel. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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17 pages, 2497 KiB

Open AccessArticle

The Combined Magneto Hydrodynamic and Electric Field Effect on an Unsteady Maxwell Nanofluid Flow over a Stretching Surface under the Influence of Variable Heat and Thermal Radiation

by Hameed Khan, Muhammad Haneef, Zahir Shah, Saeed Islam, Waris Khan and Sher Muhammad

Appl. Sci. 2018, 8(2), 160; https://doi.org/10.3390/app8020160 - 24 Jan 2018

Cited by 78 | Viewed by 5611

Abstract

The manuscript is a presentation of the combined effect of magnetic and electric field on unsteady flow of Maxwell nanofluid over a stretching surface with thermal radiations. The flow of Maxwell nanofluid is assumed to be in an unsteady state. The basic governing [...] Read more.

The manuscript is a presentation of the combined effect of magnetic and electric field on unsteady flow of Maxwell nanofluid over a stretching surface with thermal radiations. The flow of Maxwell nanofluid is assumed to be in an unsteady state. The basic governing equations changed to a group of differential equations, using proper similarity variables. The obtained modeled equations are nonlinear and coupled. An optimal approach is used to acquire the solution of the modeled problem analytically. The effects of electric field, magnetic field and thermal radiations on Maxwell nanofluid are the main focus in this study. The impact of the Skin friction on velocity profile, Nusselt number on temperature profile and Sherwood number on concentration profile are studied numerically. The influential behavior of the unsteady parameter

λ,

magnetic parameter

M,

electric parameter

E,

radiation parameter

R d,

Maxwell parameter

β,

thermophoresis parameter

N t,

Prandtl number

\Pr,

Schmidt number

S c,

space dependent coefficient

A

and temperature dependent coefficient

B

on the velocity

f (h),

concentration

ϕ (η)

and temperature

θ (η)

are analyzed and studied. The consequences are drawn graphically to see the physical significance of the problem. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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Review

Jump to: Editorial, Research

30 pages, 11595 KiB

Open AccessReview

Preparation Techniques of TiO₂ Nanofluids and Challenges: A Review

by Hafiz Muhammad Ali, Hamza Babar, Tayyab Raza Shah, Muhammad Usman Sajid, Muhammad Arslan Qasim and Samina Javed

Appl. Sci. 2018, 8(4), 587; https://doi.org/10.3390/app8040587 - 8 Apr 2018

Cited by 240 | Viewed by 17398

Abstract

Titanium dioxide (TiO₂) has been used extensively because of its unique thermal and electric properties. Different techniques have been used for the preparation of TiO₂ nanofluids which include single-step and two-step methods. In the natural world, TiO₂ exists in [...] Read more.

Titanium dioxide (TiO₂) has been used extensively because of its unique thermal and electric properties. Different techniques have been used for the preparation of TiO₂ nanofluids which include single-step and two-step methods. In the natural world, TiO₂ exists in three different crystalline forms as anatase, brookite, and rutile. Nanoparticles are not used directly in many heat transfer applications, and this provides a major challenge to researchers to advance towards stable nanofluid preparation methods. The primary step involved in the preparation of nanofluid is the production of nano-sized solid particles by using a suitable technique, and then these particles are dispersed into base fluids like oil, water, paraffin oil or ethylene glycol. However, nanofluid can also be prepared directly by using a liquid chemical method or vapor deposition technique (VDT). Nanofluids are mostly used in heat transfer applications and the size and cost of the heat transfer device depend upon the working fluid properties, thus, in the past decade scientists have made great efforts to formulate stable and cost-effective nanofluids with enhanced thermophysical properties. This review focuses on the different synthesis techniques and important physical properties (thermal conductivity and viscosity) that need to be considered very carefully during the preparation of TiO₂ nanofluids for desired applications. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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