Experimental Investigation on Preparation and Stability of Al2O3 Nanofluid In Deionized Water and Ethylene Glycol

Nanofluid has the potential as a cooling medium for the next generation fluid as it possesses many advantages in many engineering applications. However, one of the main challenges is to establish a well-dispersed nanoparticles system in a base fluid. The preparation technique of nanofluid plays an important part as it influences the measurement of thermal conductivity. Therefore, the objectives of this study are to evaluate the nanoparticle dispersion in different base fluid compositions and to determine the optimized suspension sonication time. In detail, 0.2 wt.% of Al2O3 nanofluid stability in the three ratios of base fluid (deionized water:ethylene glycol) 80:20, 70:30 and 60:40 were studied. The studies were based on a visual inspection and spectral absorbance analysis. It has clearly shown that the nanofluids prepared in 60:40 base fluid within 3 hours sonication time was the most stable suspension compared to other nanofluids. The visual inspection indicated nanofluid condition remains stable after 30 days. The spectral absorbance of nanofluids was recorded at 100 % for 5 days after preparation and remains above 95 % compared to the initial value, reflecting stable suspension. Hence the novelty of this work lies in the nanofluid stability based on sonication time and base fluid compositions.

Download Full-text

Entropy Generation and Thermal Analysis of Nanofluid Flow Inside the Evacuated Tube Solar Collector

10.21203/rs.3.rs-967559/v1 ◽

2021 ◽

Author(s):

S. Mojtaba Tabarhoseini ◽

M. Sheikholeslami

Keyword(s):

Heat Transfer ◽

Entropy Generation ◽

Solar Collector ◽

Base Fluid ◽

Pure Water ◽

Working Fluid ◽

Distribution Analysis ◽

Nanoparticle Dispersion ◽

Evacuated Tube Solar Collector ◽

Evacuated Tube

Abstract In the current investigation, the thermal and thermodynamic behavior of a buoyancy-driven evacuated tube solar collector has undergone precise evaluation, and the efficacy of nanoparticle dispersion in the base fluid has been scrutinized using computational fluid dynamics based on the finite volume method. The natural convection process was analyzed in different vertical sections of the absorber tube. The temperature and velocity distributions of water as the conventional working fluid and the nanofluid were compared at various cutting planes along the tube during the simulation time. In this problem, CuO nanoparticles with optimum thermal properties were suspended in the base fluid. According to the surveyed results, the temperature distribution analysis illustrates that the mean temperature of the tank experiences more enhancement when the nanofluid is used. The comparison of the heat transfer coefficient between two simulated cases shows the competency of utilizing CuO/water nanofluid in the thermal performance improvement of the collector. The results related to entropy generation assessment show that the irreversibility owing to fluid friction rises when the nanofluid is applied during the flow time. In contrast, the entropy generation of pure water owing to heat transfer surpasses the case with nanofluid.

Download Full-text

Experimental Evaluation on Tribological Performance of the Wheel/Workpiece Interface in NMQL Grinding With Different Concentrations of Al2o3 Nanofluids

Enhanced Heat Transfer Mechanism of Nanofluid MQL Cooling Grinding - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-7998-1546-4.ch014 ◽

2020 ◽

pp. 317-336

Keyword(s):

Base Fluid ◽

Grinding Wheel ◽

Low Carbon ◽

Machining Performance ◽

Force Ratio ◽

Lubrication Performance ◽

Transfer Capability ◽

Green Lubricant ◽

Al2o3 Nanofluid

As a result of the growing need for environmental protection and the increasing number of health problems faced by workers, traditional lubricants are gradually being replaced. Nanofluids, which contain nanoparticles in the proper base fluid, can serve as a low carbon, “green” lubricant. Nanofluids show improved heat transfer capability and lubricating properties. Therefore, increasing lubricating effects is an effective way to improve machining performance. The tribological properties of grinding wheel/workpiece interface with different concentration of Al2O3 nanofluid micro-lubrication grinding were studied. The influences of the force ratio, viscosity and contact angle of Al2O3 nanofluids with different concentrations on the grinding force and the surface quality of workpieces are discussed. The best concentration of Al2O3 nanofluid with good lubrication performance in grinding zone was obtained.

Download Full-text

Effect of moisture and sonication time on dielectric strength and heat transfer performance of transformer oil based Al2O3 nanofluid

International Journal of Advanced Technology and Engineering Exploration ◽

10.19101/ijatee.2021.874258 ◽

2021 ◽

Vol 8 (82) ◽

pp. 1222-1233

Author(s):

S. Ravi Babu ◽

N.V.A Ravi Kumar ◽

P. Ramesh Babu

Keyword(s):

Heat Transfer ◽

Heat Transfer Performance ◽

Dielectric Strength ◽

Transformer Oil ◽

Transfer Performance ◽

Sonication Time ◽

Effect Of Moisture ◽

Al2o3 Nanofluid

Download Full-text

Experimental Evaluation on Tribological Performance of the Wheel/Workpiece Interface in NMQL Grinding With Different Concentrations of Al2o3 Nanofluids

Research Anthology on Synthesis, Characterization, and Applications of Nanomaterials ◽

10.4018/978-1-7998-8591-7.ch067 ◽

2021 ◽

pp. 1608-1627

Author(s):

Changhe Li ◽

Hafiz Muhammad Ali

Keyword(s):

Base Fluid ◽

Grinding Wheel ◽

Low Carbon ◽

Machining Performance ◽

Force Ratio ◽

Lubrication Performance ◽

Transfer Capability ◽

Green Lubricant ◽

Al2o3 Nanofluid

Download Full-text

Numerical Simulation of Water as Base Fluid Dispersed by Al2O3 Aluminum Oxide Nano-Sized Solid Particles with Various Concentrations

Annales de Chimie Science des Matériaux ◽

10.18280/acsm.440401 ◽

2020 ◽

Vol 44 (4) ◽

pp. 231-238

Author(s):

Chafika Zidani ◽

Rachid Maouedj ◽

Mohamed Salmi

Keyword(s):

Base Fluid ◽

Computational Approach ◽

Field Structure ◽

Current Speed ◽

Solid Particles ◽

Two Dimensional ◽

Flow Disturbance ◽

Flow Rates ◽

Internal Surfaces ◽

Al2o3 Nanofluid

Curves of pressure, lines of current, speed of fluid, fields and diagrams of kinetic energy, and plots of viscosity through a H2O/Al2O3 nanofluid-heat exchanger with recirculation promoters are studied by using a computational approach and a two-dimensional algorithm. The simulation used four nanofluid fractions, i.e. ϕ = 0.5, 1, 2 and 4 percent, with four flow rates, i.e. Re = 5, 10, 15 and 20 (× 103). Both the discontinuous-type deflectors and the detached-model bars are considered to reinforce the nanofluid field structure. The discontinuous-situation of these deflectors allows reducing the pressure on its front-corner by passing the fluid between their internal surfaces. In addition, the field is detached from the front-sharp-edge, forcing the creation of recycling-rings on their back-areas. While, the presence of the detached-bar model in both the top and the lower stations of the exchanger allows an improvement in the flow disturbance across the gaps through their interior-surfaces, and the formation of new recycling-cells near their right-sides. These vortices constitute opposite-currents where their strength increases with increasing nanofluid concentration and Reynolds values.

Download Full-text

Convective Transport in Nanofluids

Journal of Heat Transfer ◽

10.1115/1.2150834 ◽

2005 ◽

Vol 128 (3) ◽

pp. 240-250 ◽

Cited By ~ 3085

Author(s):

J. Buongiorno

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Boundary Layer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Base Fluid ◽

Convective Transport ◽

Brownian Diffusion ◽

Nanoparticle Dispersion ◽

Transfer Coefficients

Nanofluids are engineered colloids made of a base fluid and nanoparticles (1-100nm). Nanofluids have higher thermal conductivity and single-phase heat transfer coefficients than their base fluids. In particular, the heat transfer coefficient increases appear to go beyond the mere thermal-conductivity effect, and cannot be predicted by traditional pure-fluid correlations such as Dittus-Boelter’s. In the nanofluid literature this behavior is generally attributed to thermal dispersion and intensified turbulence, brought about by nanoparticle motion. To test the validity of this assumption, we have considered seven slip mechanisms that can produce a relative velocity between the nanoparticles and the base fluid. These are inertia, Brownian diffusion, thermophoresis, diffusiophoresis, Magnus effect, fluid drainage, and gravity. We concluded that, of these seven, only Brownian diffusion and thermophoresis are important slip mechanisms in nanofluids. Based on this finding, we developed a two-component four-equation nonhomogeneous equilibrium model for mass, momentum, and heat transport in nanofluids. A nondimensional analysis of the equations suggests that energy transfer by nanoparticle dispersion is negligible, and thus cannot explain the abnormal heat transfer coefficient increases. Furthermore, a comparison of the nanoparticle and turbulent eddy time and length scales clearly indicates that the nanoparticles move homogeneously with the fluid in the presence of turbulent eddies, so an effect on turbulence intensity is also doubtful. Thus, we propose an alternative explanation for the abnormal heat transfer coefficient increases: the nanofluid properties may vary significantly within the boundary layer because of the effect of the temperature gradient and thermophoresis. For a heated fluid, these effects can result in a significant decrease of viscosity within the boundary layer, thus leading to heat transfer enhancement. A correlation structure that captures these effects is proposed.

Download Full-text

Contrast from epitaxially sandwiched macromolecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081991 ◽

1978 ◽

Vol 36 (2) ◽

pp. 226-227

Author(s):

M. Talianker ◽

D.G. Brandon

Keyword(s):

Gold Film ◽

Lattice Defect ◽

Gold Foil ◽

Specimen Preparation ◽

Preparation Technique ◽

Resolution Limit ◽

Transmission Electron ◽

Crystal Lattice Defect ◽

Void Effect ◽

Lattice Resolution

A new specimen preparation technique for visualizing macromolecules by conventional transmission electron microscopy has been developed. In this technique the biopolymer-molecule is embedded in a thin monocrystalline gold foil. Such embedding can be performed in the following way: the biopolymer is deposited on an epitaxially-grown thin single-crystal gold film. The molecule is then occluded by further epitaxial growth. In such an epitaxial sandwich an occluded molecule is expected to behave as a crystal-lattice defect and give rise to contrast in the electron microscope.The resolution of the method should be limited only by the precision with which the epitaxially grown gold reflects the details of the molecular structure and, in favorable cases, can approach the lattice resolution limit.In order to estimate the strength of the contrast due to the void-effect arising from occlusion of the DNA-molecule in a gold crystal some calculations were performed.

Download Full-text

The ionic strength dependence of chromatin folding

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081966 ◽

1978 ◽

Vol 36 (2) ◽

pp. 220-221

Author(s):

F. Thoma ◽

TH. Koller

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Ionic Strength ◽

Specimen Preparation ◽

Preparation Technique ◽

Carbon Supports ◽

Ionic Strength Dependence ◽

Chromatin Folding ◽

Strength Dependence ◽

Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

Download Full-text

SEM evaluation of the TEM cold-stage double-film specimen

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111471 ◽

1984 ◽

Vol 42 ◽

pp. 272-273

Author(s):

Jayesh Bellare

Keyword(s):

Spatial Distribution ◽

Sample Preparation ◽

Sample Thickness ◽

Specimen Preparation ◽

Preparation Technique ◽

Liquid Sample ◽

Thin Specimen ◽

Sample Preparation Technique ◽

Cold Stage ◽

Film Specimen

Seeing is believing, but only after the sample preparation technique has received a systematic study and a full record is made of the treatment the sample gets.For microstructured liquids and suspensions, fast-freeze thermal fixation and cold-stage microscopy is perhaps the least artifact-laden technique. In the double-film specimen preparation technique, a layer of liquid sample is trapped between 100- and 400-mesh polymer (polyimide, PI) coated grids. Blotting against filter paper drains excess liquid and provides a thin specimen, which is fast-frozen by plunging into liquid nitrogen. This frozen sandwich (Fig. 1) is mounted in a cooling holder and viewed in TEM.Though extremely promising for visualization of liquid microstructures, this double-film technique suffers from a) ireproducibility and nonuniformity of sample thickness, b) low yield of imageable grid squares and c) nonuniform spatial distribution of particulates, which results in fewer being imaged.

Download Full-text

Ultramicrotomy as a Technique for Materials Specimen Preparation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135745 ◽

1990 ◽

Vol 48 (2) ◽

pp. 428-429

Author(s):

S.R. Glanvill

Keyword(s):

Materials Science ◽

Structural Information ◽

Specimen Preparation ◽

Preparation Technique ◽

Cross Sectional ◽

Surfaces And Interfaces ◽

Beam Analysis ◽

Flat Embedding ◽

20 Nm ◽

Sectional Analysis

This paper summarizes the application of ultramicrotomy as a specimen preparation technique for some of the Materials Science applications encountered over the past two years. Specimens 20 nm thick by hundreds of μm lateral dimension are readily prepared for electron beam analysis. Materials examined include metals, plastics, ceramics, superconductors, glassy carbons and semiconductors. We have obtain chemical and structural information from these materials using HRTEM, CBED, EDX and EELS analysis. This technique has enabled cross-sectional analysis of surfaces and interfaces of engineering materials and solid state electronic devices, as well as interdiffusion studies across adjacent layers.Samples are embedded in flat embedding moulds with Epon 812 epoxy resin / Methyl Nadic Anhydride mixture, using DY064 accelerator to promote the reaction. The embedded material is vacuum processed to remove trapped air bubbles, thereby improving the strength and sectioning qualities of the cured block. The resin mixture is cured at 60 °C for a period of 80 hr and left to equilibrate at room temperature.

Download Full-text