Volume Fraction Of Alumina Research Articles

Nonsimilar solution of hybrid nanofluid over curved stretching surface with viscous dissipation: A numerical study

In this research work, numerical simulations and mathematical modeling are introduced for the mixed convection hybrid nanofluid flow over a curved stretching surface. The energy equation is modeled subjected to viscous dissipation, a heat source with radiative heat flow. Convective and velocity slip conditions are assumed at the stretchable surface. The Eckert number and Grashof number contained the independent variable "s" which is not suitable for the dimensionless parameters. In this regard, the problem is solved by a nonsimilar approach. The nonsimilar approach has not been tried before on a curved stretching surface. Furthermore, alumina and copper are taken as nanoparticles, and blood is taken as a base fluid. A nonsimilarity transformation is used to transform the governing equation into dimensionless (PDEs). Converting these PDEs into ODEs by using the local nonsimilarity method. The familiar Bvp4c is used to perform numerical computations for a dimensionless nonlinear system. Significant results for velocity and temperature profiles for different parameters are comprehensively presented and discussed. Results indicated that increasing the volume fraction of the base fluid increased the fluid velocity and temperature. The volume fraction of alumina and copper nanoparticles decreases the fluid velocity and boundary layer thickness. Furthermore, the slip condition decreases the fluid velocity, and the fluid becomes static if the slip parameter value is greater than fifty.

Analyzing performance of energy storage system during discharging with loading nanoparticle for enhancing the treatment of water

Current article is about the solidification process of water through the complex container. The geometry has extended cold surfaces with complex shapes. The base PCM was mixed with nano-powders to enhance the thermal feature of water. The final model for presentation of freezing contains two equations for predicting the values of temperature and solid fraction. The forms of equations are unsteady and Galerkin method applied for solving them. As volume fraction of alumina enhances, the freezing rate enhances around 41.2 %. With reducing the concentration from 0.04 to 0.02, the freezing time augments about 24.09 % and this percentage for the middle size of particles is 5.3 times greater than that of the biggest powders. The increase of diameter up to 40 nm makes the period to drop by 19.97 %.

Two-Dimensional Magnetized Mixed Convection Hybrid Nanofluid Over a Vertical Exponentially Shrinking Sheet by Thermal Radiation, Joule Heating, Velocity and Thermal Slip Conditions

Hybrid nanofluid is an improved kind of nanofluid that typically utilized to enhance the thermal efficiency in fluid flow regimes. It has a wide range of real-world applications. This opened up many new prospects to further investigate the two-dimensional hybrid nanofluid under different body geometries and physical parameters. A numerical study of a two-dimensional magnetized mixed convection hybrid nanofluid flow over a vertical exponentially shrinking sheet is considered in this paper. The main objective of this current study is to examine the influences of volume fraction of copper, mixed convection, and radiation on the reduced skin friction and reduced heat transfer against the effect of suction. Besides, the influences of radiation, volume fraction of alumina, velocity slip, thermal slip, magnetic parameter, and Eckert number on the velocity and temperature profiles are also considered in this paper. The governing system of partial differential equations (PDEs) is transformed into a system of nonlinear ordinary differential equations (ODEs) through exponential similarity variables. Then, the bvp4c solver for MATLAB is used to solve the transformed nonlinear ODEs. Numerous significant results are being observed. As the quantity of mixed convection was raised, the reduced skin friction improved in both solutions, and reduced heat transfer increased in the second solution but with no variation found in the first solution. Besides, the temperature profile grew when the volume fraction of alumina, radiation, magnetic parameter, and Eckert number were raised in both solutions. In terms of heat transfer rate, when the amount of the velocity slip parameter was increased, temperature reduced in the first solution but increased in the second solution. Whilst temperature dropped in both solutions as the thermal slip parameter was enhanced. In conclusion, the addition of hybrid nanoparticles boosted the heat transmission rate. In the assisting flow condition, dual solutions exist when the suction parameter value is greater or equal to its critical point. However, no fluid flow is conceivable when the indicated value is less than this critical point.

MHD stagnation-point flow of nanofluid due to a shrinking sheet with melting, viscous dissipation and Joule heating effects

Nanofluids have received a lot of interest in recent years because of their prospective uses in industrial applications; therefore, a progressive study on flow control is requirable. The primary goal of this study is to elucidate the magnetohydrodynamic (MHD) stagnation point flow of alumina-water nanofluid due to a shrinking sheet with the inclusion of viscous dissipation, melting and Joule heating effects. The similarity transformation reduces the complexity of the model into the similarity (ordinary) differential equations. The findings are numerically acquired by programming the resultant equations in MATLAB and processing them via the bvp4c tool. The findings show that at the shrinking condition, two solutions are conceivable, with the separation of the flow occurring within this area. The examination of stability reveals that only one solution remains stable, while the other is not. By boosting the melting effect and decreasing the nanoparticle volume fraction as well as the Eckert number, it is possible to accelerate the heat transmission in the fluid flow system. The temperature profile is decelerated as the nanoparticle volume fraction amplifies, and this is accompanied by a decrease in Joule heating. This study also suggests considering 2% of alumina volume fraction instead of 1% so that the flow separation process can be delayed, and simultaneously sustain the laminar flow. The increment of melting effect by 25%, reducing the skin friction approximately by 5% at a certain degree of shrinking. This study can be referred as guidance in managing the relevant parameters imposed on the nanofluid flow, which has the capability to give significant advantages, especially in monitoring the flow performance.

Employing numerical method for evaluating the heat transfer rate of a hot tube by nanofluid natural convection

One of the major issues in industry is cooling of pipes when using forced convection mechanism is not able to cool pipes, but free convection mechanism can be a suitable method. In this regard, a half-pipe was installed in the center of a half-elliptical enclosure in which the gap of between them was saturated with nanofluid of water and alumina (aluminum oxide) nanoparticle depending on temperature and nanoparticle diameter. Several samples were simulated by means of CFD and FVM to understand the impacts of Rayleigh number, inclined angle, and volume fraction of nanoparticles on the heat flux of hot pipe. In addition, the dynamic viscosity and thermal conductivity coefficient of nanofluid depended on temperature, nanoparticle diameter, and volume fraction, which were used for precising simulation to physical results. The obtained results showed that adding 3% volume fraction of alumina could increase the average heat flux of hot half-pipe by 8.7%. Moreover, at high Rayleigh numbers, volume fraction of 1% was optimum amount for volume fraction. In addition, inclined angle had considerable influence on average heat flux, specifically, in high Rayleigh numbers. • Simulation of natural convection between a hot half-pipe and cold half-elliptical enclosure to cool hot pipe. • Dependence of nanofluid thermal conductivity and dynamic viscosity to temperature, its diameter, and volume fraction. • At high Rayleigh numbers, the optimum volume fraction is 0.01. • At R a = 10 3 a n d 10 4 , the optimal values of the inclined angle are 60 and 0°, respectively.

Analytical investigation of transient free convection and heat transfer of a hybrid nanofluid between two vertical parallel plates

Flow and heat transfer of transient free convection of a hybrid nanofluid between two parallel plates are theoretically investigated. Effects of a magnetic field, thermal radiation, and a heat source or a sink are considered. Laplace transforms are used to solve the dimensionless governing equations. Analytical expressions of velocity and temperature profiles and shear stress and rate of heat transfer are presented. Moreover, the correlations between the parameters and the shear stress and the rate of heat transfer have been derived. Increasing alumina and copper nanoparticle volume fractions reduces the velocity and temperature. However, the converse is seen for increasing heat source or sink parameter. For increasing radiation parameter, the temperature decreases but the velocity first increases. When 5% and 10% alumina nanoparticles are mixed with 5% copper nanoparticle, the heat transfer through the left wall increases about 14% and 30% and that through the right wall enhances about 21% and 44% in comparison to the heat transfer of pure fluid. For 5% and 10% copper nanoparticles with 5% alumina nanoparticle, the corresponding values are 15% and 31% and 22% and 45%, respectively. The heat source or sink intensity also plays an important role in the thermal field and heat transfer.

A Numerical Simulation of Machining 6061 Syntactic Foams Reinforced with Hollow Al2O3 Shells

Aluminum closed cell syntactic foams possess reduced density, higher peak compression strength, and lower coefficient of thermal expansion and thermal conductivity compared to metal alloys. However, the industrial mass production of these complex material systems presents a significant problem in the form of poor machinability. In order to address this concern and to increase the use of this potential cost- and energy-saving system, a two-dimensional numerical model using the AdvantEdgeTM machining software was developed. For the verification of the numerical model, machining trials in dry conditions were conducted on different samples using a SandvikTM carbide-coated insert having a 6° rake angle and a 7° clearance angle. The hollow alumina shell diameter and volume fraction were found to profoundly affect the magnitude of the generated machining forces. This study showed an increase in machining force by almost 25% for syntactic foams reinforced with hollow alumina shells of higher volume fraction and coarser diameters. The cutting conditions to obtain a favorable stress diastribution in the syntactic foam’s machined sub-surface were identified.

Shaping of alumina microbeads by drop-casting of the photopolymerizable suspension into silicone oil and UV curing

The alumina microbeads were obtained by forming the drops of alumina suspensions in a silicone oil followed by UV curing. Due to the strong hydrophobic properties, silicon oil is a non-solvent (non-miscible) to the suspensions, thus the formation of perfectly rounded beads occurs spontaneously. The size of beads was controlled by a selection of a needle diameter and the position of needle tip: above or immersed in silicone oil. Thanks to that it was possible to obtain beads with diameters from 1000 to 1300 µm. The obtained alumina microbeads were characterized by quite a narrow size distribution, the differences in the size of the beads, within one series, did not exceed 1.5%. The research showed that the higher alumina volume fraction in suspensions favors the development of microstructure and thus influences mechanical properties. It was proved that the application of the methyl silicone oil as the environment responsible for the formation of the beads does not affect the sintering process.

Thermal, structural and transport properties of composite solid electrolytes (1-x)(C4H9)4NBF4–xAl2O3

Thermal, structural and electrical properties of composite solid electrolytes (1-x)(C4H9)4NBF4–xAl2O3 with nanocrystalline γ-alumina were investigated by DSC, X-ray diffraction, IR spectroscopy, impedance and electrochemical measurements. It was found that the melting enthalpy of (C4H9)4NBF4 in the composites strongly decreases and its value approaches to zero in the composites with x ≥ 0.9, where x is the molar fraction of alumina, indicating the transformation of (C4H9)4NBF4 to an interface-stabilized amorphous state. This effect was quantitatively interpreted in terms of the brick-wall model assuming that a layer of amorphous phase of the ionic salt is formed at salt/oxide interfaces. At the alumina concentration of x = 0.9, corresponding to a volume fraction of alumina f = 0.53, almost all the ionic salt gets into the interface layer the thickness of the amorphous layer is nearly 3 nm. These results agree with the results of X-ray diffraction studies and IR spectroscopy. Introduction of nanocrystalline γ-alumina into the (C4H9)4NBF4 matrix leads to a relative increase in conductivity by more than 2 orders of magnitude, conductivity goes through a maximum of 0.21 mS/cm at 130 °C for the composite with x = 0.9. This composite is characterized by a non-Arrhenius temperature dependence, typical for glassy electrolytes. It was shown that the electrochemical voltage for the composite 0.1(C4H9)4NBF4–0.9Al2O3 is nearly 4 V.

Optimization of composite bone scaffolds prepared by a new modified foam replica technique

This study aimed to demonstrate the application of the recently developed modified polyurethane (PU) foam replica technique in the fabrication of the hydroxyapatite (HA)/alumina (Al2O3) composite bone scaffolds with different volume fraction quantities of the alumina. Furthermore, the optimum values of porosity and volume fraction of the alumina were obtained in order to achieve an ideal scaffold suitable for repairing the damaged cancellous bone tissues existent in different anatomical locations of the body. Introducing a specific ageing process, samples with excellent properties suitable for bone fracture healing were produced in this study. 20 different groups of the scaffolds, each one comprising 20 samples, which included specimens with different porosities and compositions, were synthesized and characterized regarding morphology, composition, porosity, and mechanical properties. The field emission scanning electron microscopy (FESEM) and nano-computed tomography (nano-CT) images of the samples demonstrated that the scaffolds with high value of porosity and interconnectivity between the pores were achieved via the proposed scheme. According to the findings, although the overall trend of the variation in the viscosity of different HA/Al2O3 slurry compositions during the ageing process were the same, their ageing time was different. Besides, depending on the volume fraction of the alumina and the porosity of the foams used in synthesis of the samples, the values of the porosity and the compressive strength of the scaffolds were varied from 55.72% to 84.76% and 1.67–7.13 MPa, respectively, which are good for bone tissue engineering applications. Moreover, the results obtained from the optimization process revealed that the scaffolds with the respective values of the porosity and the alumina volume fraction of 84.76% and 0% for lumbar spine, 62.83% and 6.57% for proximal tibia, 56.16% and 9.33% for proximal femoral, and 55.72% and 9.8% for femur are the best choices for healing the corresponding injured spongy bone tissues.

Effect of powder metallurgy process parameters on tribology and micro hardness of Al6063- nano Al2O3 MMCs

The effect of powder metallurgy process parameters and aging on the hardness and wear properties of nano Al2O3 reinforced Al 6063 MMCs is investigated. Mechanical milling and blending of various volume fractions of nano Alumina in the base Al 6063 matrix followed by hot uniaxial powder compaction was used to produce the test samples. OHNS die with a punch of required diameter was used to produce the test samples. The hardness and wear behavior of the samples were studied under various process parameters such as different compaction durations and compaction pressures. Apart from the experimental investigations, MANOVA analysis was employed to study the effect of the different input variables on the output viz., hardness and wear rate. VHN tests showed an enhancement in hardness up to the addition of 6 vol% of nano Alumina beyond which a declining trend was observed. Wear rate improved with the increase in the addition of nano Alumina, and it was least for the samples produced at a compaction duration of 60 min, whereas maximum wear for the samples produced at 90 min compaction duration. A commendable enhancement of hardness and wear behavior was also observed on account of the aging of the samples.

Forced Convection of Non-Newtonian Nanofluid Flow over a Backward Facing Step with Simultaneous Effects of Using Double Rotating Cylinders and Inclined Magnetic Field

The forced convection of non-Newtonian nanofluid for a backward-facing flow system was analyzed under the combined use of magnetic field and double rotating cylinders by using finite element method. The power law nanofluid type was used with different solid volume fractions of alumina at 20 nm in diameter. The effects of the Re number (100≤Re≤300), rotational Re number (−2500≤Rew≤3000), Ha number (0≤Ha≤50), and magnetic field inclination (0≤γ≤90) on the convective heat transfer and flow features were numerically assessed. The non-Newtonian fluid power law index was taken between 0.8 and 1.2 while particle volume fractions up to 4% were considered. The presence of the rotating double cylinders made the flow field complicated where multiple recirculation regions were established near the step region. The impacts of the first (closer to the step) and second cylinders on the heat transfer behavior were different depending upon the direction of rotation. As the first cylinder rotated in the clockwise direction, the enhancement in the average heat transfer of 20% was achieved while it deteriorated by approximately 2% for counter-clockwise directional rotation. However, for the second cylinder, both the rotational direction resulted in heat transfer augmentation while the amounts were 14% and 18% at the highest speeds. Large vortices on the upper and lower channel walls behind the step were suppressed with magnetic field effects. The average Nu number generally increased with the higher strengths of the magnetic field and inclination. Up to 30% increment with strength was obtained while this amount was 44% with vertical orientation. Significant impacts of power law fluid index on the local and average Nu number were seen for an index of n = 1.2 as compared to the fluid with n = 0.8 and n = 1 while an average Nu number of 2.75 times was obtained for the flow system for fluid with n = 1.2 as compared to case for fluid with the n value of 0.8. Further improvements in the local and average heat transfer were achieved with using nanoparticles while at the highest particle amount, the enhancements of the average Nu number were 34%, 36% and 36.6% for the fluid with n values of 0.8, 1 and 1.2, respectively.

Performance analysis of thermoelectric generator mounted chaotic channel by using non-Newtonian nanofluid and modeling with efficient computational methods

Performance features of a thermoelectric system mounted in a chaotic channel with non-Newtonian power law fluid are numerically explored with finite element method. The analysis is performed for different values of Re number of the hot and cold fluid streams (250⩽Re⩽1000), power law indices (0.75⩽n⩽1.25) and solid volume fraction of alumina (0⩽ϕ⩽4%) in water. It is observed that the fluid type with different power law indices significantly affected the electric potential variations and power generation of the thermoelectric system. Impacts of Re number on the power generation enhancement amount depends upon the power law index. The power rises by about 123.78%, 94.13% and 52.30% at the highest Re for different power law index combinations of (0.75,0.75), (0.75,12.5) and (1.25,1.25), respectively. Thermoelectric power reduces by about 39.71% for shear thinning fluids in both channels while it rises by about 43.48% for shear thickening fluids in chaotic channels. The potential of using nanofluids is more when both channels contain shear thinning fluids. Nanofluids rise the power of thermoelectric system by about 31%, 29% and 28% for the case when the hot side fluid is shear thinning, Newtonian and shear thickening fluid types while the cold side chaotic channel is shear thinning. When constant and varying interface temperature configurations are compared, there is at most 3% variations in the generated power while the trends in the curves for varying parameters are similar. The computational cost of constant interface temperature and computations only in the thermoelectric domains are much cheaper as compared to high fidelity coupled computational fluid dynamics simulations. The temperature field in the whole computational domain is approximated by using POD based approach with nine modes. A polynomial type regression model is used for POD-modal coefficients while fast and accurate results for interface temperatures are obtained.

Mixed convection flow of viscoelastic Ag-Al2O3 /water hybrid nanofluid past a rotating disk

An exploration is carried out to inspect mixed convection flow of viscoelastic hybrid nanofluid past a rotating disk under slip and convective heating condition influences. As the hybrid nanoparticles, and silver (Ag) are considered with carboxymethyl cellulose (CMC) - water with low concentration () preferred as a base fluid. The viscoelastic (non-Newtonian) fluid model is assumed in favor of hybrid nanofluids applying magnetic field influences normal to the flow of fluid. The nonlinear ordinary differential equations get a hold from the governing equations are simplified using suitable similitude into dimensionless from and are solved via the influential method called Galerkin finite element method. The roles of physical parameters on radial and tangential velocities, temperature and concentration are exhibited graphically with their physical features. The results show that enrichment in the values of Grashof number be inclined to develop buoyancy forces which speed up the motion of fluid and tends to increases radial and tangential velocity fields but it imposes to decline temperature and concentration profile. Also, the outcome confirms that the distribution of temperature and concentration can be controlled with higher alumina and silver nanoparticles volume fraction. Moreover, the effects of thermal Grashof number, volume fraction of alumina and silver nanoparticles on skin friction coefficients, Nusselt number and Sherwood number are numerically discussed through tables. It also corroborates that 3% vol. fraction of and Ag nanoparticles has the greatest − than 1% vol. fraction of and Ag nanoparticles.

Marangoni hybrid nanofluid flow over a permeable infinite disk embedded in a porous medium

The importance of porous medium and hybrid nanofluid in the augmentation of heat transfer process has been realized by the researchers. Hence, a numerical boundary layer exploration towards Marangoni hybrid nanofluid flow over a permeable infinite disk placed in a porous medium is carried out. 1% volume fraction of alumina is hybridized with (0.01 − 1)% volume fraction of copper in the water. The solver in Matlab software (bvp4c) is applied to enumerate the solutions. The non-unique (dual) solutions are discoverable for the shrinking disk and only the first solution is real. The upsurges of copper volume fraction, porosity and suction parameters enable the heat transfer rate to enhance and decelerate the boundary layer bifurcation at the shrinking disk.

Analysis of Forced Convection heat transfer in laminar flow through a compact pipe filled with Nanofluids using CFD

In this paper, a Numerical investigation of developing laminar flows with forced convection through a compact circular pipe has been done using water-Al2O3 nano-fluid. Uniform heat flux (UHF) and the steady-state has been maintained at the wall in each model. Throughout the numerical experiments, Nano-fluid models were made by Alumina volume fraction and were processed under the Re=1050. A single-phase fluid model was determined by nano-fluid thermal and physical properties calculation, whereas the Two-phase model, i.e., granular mixture model was defined in 100nm diameter. The results show that the Al2O3 volume fraction increases, the heat transfer rate and Nusselt number increases. All the numerical simulations were developed in ANSYS FLUENT. The result displays the rise of thermal transfer from the volume fraction concentration.

Heat transfer analysis of micropolar hybrid nanofluid over an oscillating vertical plate and Newtonian heating

The unsteady flow of micropolar hybrid nanofluids through an oscillating vertical plate having infinite length has been analyzed in this study. This flow goes through Newtonian heating and thermal radiation. To enrich the thermal properties, we add copper and alumina nanoparticles to micropolar fluid. For the enhancement of heat transfer, water is taken as base liquid. The dimensionless reduced form of the governing equations for velocity, temperature and microrotation is formed by using dimensional analysis. We used Laplace transform method to have the exact solutions of these governing equations. MathCad’s software has been used to visualize the effects on the flow of fluid graphically. We found that microrotation, velocity and temperature are inversely proportional to Prandtl number but directly proportional to Grashof number. Further, temperature can be enhanced for increasing value of Newtonian heating, radiation and volume fraction of nanoparticles copper and alumina.

Acoustic Matching Layer Films Using B-Stage Thermosetting Polymer Resins for Ultrasound Transducer Applications.

Acoustic matching layer films (MLFs) were fabricated using B-stage thermosetting polymer resins with various volume fractions of alumina and tungsten powders. After making certain thickness MLFs, ultrasonic matching layers were fabricated using a simple molding process. The thickness of the matching layers can be precisely adjusted from several micrometer to hundreds of micrometer, without any grinding process. Experimental values of acoustic impedances of the matching layers were in good agreement with theoretical values calculated by the Devaney model. Using the optimized acoustic matching layer by the MLFs, the maximum intensity and the fractional bandwidth of the ultrasonic transducer were increased by 10% and 37% respectively. The effectiveness of the matching layer using MLFs was successfully verified.

Flow and heat transfer of a hybrid nanofluid past a permeable moving surface

A steady flow and heat transfer of a hybrid nanofluid past a permeable moving surface is investigated. In this study, 0.1 solid volume fraction of alumina (Al2O3) is fixed, then consequently, various solid volume fractions of copper (Cu) are added into the mixture with water as the base fluid to form Cu-Al2O3/water hybrid nanofluid. The similarity equations are obtained by converting the governing equations of the hybrid nanofluid using the technique of similarity transformation. The bvp4c function available in Matlab software is used to solve the similarity equations numerically. The numerical results are obtained for selected parameters and discussed in detail. It is found that hybrid nanofluid enhances the heat transfer rate compared to the regular nanofluid. The results show that two solutions exist up to a certain value of the moving parameter and suction strengths. The critical value in which the solution is in existence decreases as nanoparticle volume fractions increase. The temporal stability analysis is conducted in determining the stability of the dual solutions, and it is revealed that only one of them is stable and physically reliable.

Synthesis and Characterization of Sintered Magnetic Abrasive Particles having Alumina and Carbonyl Iron Powder

The present workis focused on compacting, sintering, and characterization of sintered magnetic abrasive particles, which is composed of equal volume fraction of alumina and carbonyl iron powder. Powder metallurgy method is a well-developed technique for manufacturing of ferrous and nonferrous parts. AhO3–CIP composites are prepared through powder metallurgy method. Ball milling is used for mixing powders, and hydraulic Jack with die is used for compacting purpose. Solid and liquid phase sintering is performed at a high temperature tubular furnace under an inert gas atmosphere of argon. Solid and liquid phase sintering is done at 1000°C and 1545°C, respectively in proper consecutive sintering cycle. After sintering, the sintered pallets are crushed using ball miller to obtain the required size of the sintered powder. Energy Dispersive X-ray spectroscopy is used for elemental composition of all sintered powders. Vibrating sample magnetometer is used to see the magnetization of the particles. The saturation magnetization of the sintered abrasive obtained at 9–ton compaction pressure is found to be highest. Different phases of all prepared samples are studied using the X-ray diffraction technique. The morphology, as well as particle size, are studied using a scanning electron microscope. Also, the microstructure of sintered powders is studied using an optical microscope. Compression strength test of all sintered pallets is carried out using Universal Testing Machine. Bulk density of the pallets is measured using standard Archimedean principle. It is observed that the bulk density value increases with the compaction load. Micro hardness of the sintered pallets is measured using a Vickers micro hardness measuring instrument. The sintered pallet, fabricated at a compaction pressure of 9 ton shows the highest hardness.