scholarly journals Experimental Measurements on the Thermal Conductivity of Glycerol-Based Nanofluids with Different Thermal Contrasts

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mohamed Lotfi ◽  
Rodolphe Heyd ◽  
Abderrahim Bakak ◽  
Abdellah Hadaoui ◽  
Abdelaziz Koumina
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Volume Fraction ◽  
High Viscosity ◽  
Copper Oxides ◽  
Nanoparticle Volume Fraction ◽  
Graphene Flake ◽  
Temperature Oscillations ◽  
Graphene Flakes ◽  
3Ω Technique

We report, in this work, our study of the thermal conductivity of high-viscosity nanofluids based on glycerol. Three nanofluids have been prepared with different thermal contrasts, by suspending graphene flakes, copper oxides, or silica nanoparticles in pure glycerol. The nanofluids were thermally characterized at room temperature with the 3ω technique, with low amplitudes of the temperature oscillations. A significant enhancement of the thermal conductivity is found in both the glycerol/copper oxide and the glycerol/graphene flake nanofluids. Our results question the role played by the Brownian motion in the microscopic mechanisms of the thermal conductivity of high-viscosity glycerol-based nanofluids. A similar behavior of the thermal conductivity as a function of the nanoparticle volume fraction was found for all three glycerol-based nanofluids presently investigated. These results could be explained on the basis of fractal aggregation in the nanofluids.

Thermo-Physical Properties of Copper Matrix Composites Reinforced with 3D-SiC Network

2010 ◽  
Vol 150-151 ◽  
pp. 144-149
Author(s):  
Hong Wei Xing ◽  
Jin Song Zhang ◽  
Xiao Ming Cao
Keyword(s):  
Thermal Conductivity ◽  
Physical Properties ◽  
Room Temperature ◽  
Volume Fraction ◽  
Copper Matrix ◽  
High Thermal Stability ◽  
Matrix Composites ◽  
Copper Matrix Composites ◽  
Specific Heat Capacities ◽  
Thermo Physical Properties

Copper matrix composites reinforced with 3D-SiC network (15v% and 20v% SiC) were fabricated by squeezing copper alloy into 3D-SiC network preforms. The thermo-physical properties of the copper matrix composites were investigated. The specific heat capacities of the composites were about 0.39~0.50 J•g-1•K-1. The coefficients of thermal expansion (CTEs) of the composites were found to be lower than 6.9×10-6 -1 at Room Temperature. The composites exhibited high thermal stability for 3D-SiC network advent. The thermal conductivity of the composites was in the range of 50~80W•m−1•K−1. The thermo-physical properties of Cu matrix composites had a great relationship with the structures of 3D-SiC network preforms. The thermal conductivity of the composites decreased with an increase in the volume fraction of SiC or the structures of the limbs changing compacted, but the CTEs were not completely according this rule.

Experimental Measurement of Thermophysical Properties of Alumina- MWCNTs/Salt–Water Hybrid Nanofluids

2020 ◽  
Vol 16 (5) ◽  
pp. 734-747 ◽  
Author(s):  
Amir Hossein Sharifi ◽  
Iman Zahmatkesh ◽  
Fatemeh F. Bamoharram ◽  
Amir Hossein Shokouhi Tabrizi ◽  
Safieh Fazel Razavi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Salt Concentration ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Volume Fraction ◽  
Ph Value ◽  
Nanoparticle Volume Fraction ◽  
Optimal Conditions ◽  
Hybrid Nanofluids

Background: Hybrid nanofluids are considered as an extension of conventional nanofluids which are prepared through suspending two or more nanoparticles in the base fluids. Previous studies on hybrid nanofluids have measured their thermal conductivity overlooking other thermophysical properties such as viscosity and electrical conductivity. Objective: An experimental investigation is undertaken to measure thermal conductivity, viscosity, and electrical conductivity of a hybrid nanofluid prepared through dispersing alumina nanoparticles and multiwall carbon nanotubes in saltwater. These properties are the main important factors that must be assessed before performance analysis for industrial applications. Methods: The experimental data were collected for different values of the nanoparticle volume fraction, temperature, salt concentration, and pH value. Attention was paid to explore the consequences of these parameters on the nanofluid’s properties and to find optimal conditions to achieve the highest value of the thermal conductivity and the lowest values of the electrical conductivity and the viscosity. Results: The results demonstrate that although the impacts of the pH value and the nanoparticle volume fraction on the nanofluid’s thermophysical properties are not monotonic, optimal conditions for each of the properties are reachable. It is found that the inclusion of the salt in the base fluid may not change the thermal conductivity noticeably. However, a considerable reduction in the viscosity and substantial elevation in the electrical conductivity occur with an increase in the salt concentration. Conclusion: With the addition of salt to a base fluid, the thermophysical properties of a nanofluid can be controlled.

Diamond-Based Metal Matrix Composites for Thermal Management Made by Liquid Metal Infiltration — Potential and Limits

2008 ◽  
Vol 59 ◽  
pp. 111-115 ◽  
Author(s):  
Ludger Weber ◽  
Reza Tavangar
Keyword(s):  
Thermal Conductivity ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Room Temperature ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Diamond Powder ◽  
Matrix Composites ◽  
Pressure Infiltration ◽  
The One

Diamond-based metal matrix composites have been made based on pure Al and eutectic Ag-3Si alloy by gas pressure infiltration into diamond powder beds with the aim to maximize thermal conductivity and to explore the range of coefficient of thermal expansion (CTE) that can be covered. The resulting composites covered roughly the range between 60 and 75 vol-% of diamond content. For the Al-based composites a maximum thermal conductivity at room temperature of 7.6 W/cmK is found while for the Ag-3Si based composites an unprecedented value of 9.7 W/cmK was achieved. The CTE at room temperature varied as a function of the diamond volume fraction between 3.3 and 7.0 ppm/K and 3.1 and 5.7 ppm/K for the Al-based and the Ag-3Si-based composites, respectively. The CTE was further found to vary quite significantly with temperature for the Al-based composites while the variation with temperature was less pronounced for the Ag-3Si-based composites. The results are compared with prediction by analytical modeling using the differential effective medium scheme for thermal conductivity and the Schapery bounds for the CTE. For the thermal conductivity good agreement is found while for the CTE a transition of the experimental data from Schapery’s upper to Schapery’s lower bound is observed as volume fraction increases. While the thermophysical properties are quite satisfactory, there is a trade-off to be made in these materials between high thermal conductivity and low CTE on the one side and surface quality and machinability on the other.

scholarly journals Mixed convection stagnation point flow of the blood based hybrid nanofluid around a rotating sphere

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Taza Gul ◽  
Basit Ali ◽  
Wajdi Alghamdi ◽  
Saleem Nasir ◽  
Anwar Saeed ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Transport ◽  
Stagnation Point ◽  
Volume Fraction ◽  
Excellent Result ◽  
Concentration Field ◽  
Hybrid Nanofluid ◽  
Nanoparticle Volume Fraction ◽  
Nanofluid Flow ◽  
Rotating Sphere

AbstractIn this new world of fluid technologies, hybrid nanofluid has become a productive subject of research among scientists for its potential thermal features and abilities, which provides an excellent result as compared to nanofluids in growing the rate of heat transport. Our purpose here is to introduce the substantial influences of magnetic field on 2D, time-dependent and stagnation point inviscid flow of couple stress hybrid nanofluid around a rotating sphere with base fluid is pure blood, $${\text{TiO}}_{2} \,\,{\text{and}}\,\,{\text{Ag}}$$ TiO 2 and Ag as the nanoparticles. To translate the governing system of partial differential equations and the boundary conditions relevant for computation, some suitable transformations are implemented. To obtain the analytical estimations for the corresponding system of differential expression, the innovative Optimal Homotopy Analysis Method is used. The characteristics of hybrid nanofluid flow patterns, including temperature, velocity and concentration profiles are simulated and analyzed in detail due to the variation in the evolving variables. Detailed research is also performed to investigate the influences of relevant constraints on the rates, momentum and heat transport for both $${\text{TiO}}_{2} + {\text{Ag}} + Blood$$ TiO 2 + Ag + B l o o d and $${\text{TiO}}_{2} + Blood$$ TiO 2 + B l o o d . One of the many outcomes of this analysis, it is observed that increasing the magnetic factor will decelerate the hybrid nanofluid flow velocity and improve the temperature profile. It may also be demonstrated that by increasing the Brownian motion factor, significant improvement can be made in the concentration field of hybrid nanofluid. The increase in the nanoparticle volume fraction from 0.01 to 0.02 in the case of the hybrid nanofluid enhances the thermal conductivity from 5.8 to 11.947% and for the same value of the nanoparticle volume fraction in the case of nanofluid enhance the thermal conductivity from 2.576 to 5.197%.

scholarly journals Homogenization of Mutually Immiscible Polymers Using Nanoscale Effects: A Theoretical Study

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Sarah Montes ◽  
Agustín Etxeberria ◽  
Javier Rodriguez ◽  
Jose A. Pomposo
Keyword(s):  
Molecular Weight ◽  
Polymer Nanocomposites ◽  
Room Temperature ◽  
Theoretical Study ◽  
Volume Fraction ◽  
Mean Field Theory ◽  
Mean Field ◽  
Nanoparticle Volume Fraction ◽  
Immiscible Polymers ◽  
Complete Miscibility

A theoretical study to investigate homogenization of mutually immiscible polymers using nanoscale effects has been performed. Specifically, the miscibility behavior of all-polymer nanocomposites composed of linear-polystyrene (PS) chains and individual cross-linked poly(methyl methacrylate)-nanoparticles (PMMA-NPs) has been predicted. By using a mean field theory accounting for combinatorial interaction energy and nanoparticle-driven effects, phase diagrams were constructed as a function of PMMA-NP size, PS molecular weight, and temperature. Interestingly, complete miscibility (i.e., homogeneity) was predicted from room temperature to 675 K for PMMA-nanoparticles with radius less than ~7 nm blended with PS chains (molecular weight 150 kDa, nanoparticle volume fraction 20%) in spite of the well-known immiscibility between PS and PMMA. Several nanoscale effects affecting miscibility in PMMA-NP/PS nanocomposites involving small PMMA-nanoparticles are discussed.

Thermal Conductivity of Nanochanneled Alumina

2000 ◽  
Author(s):  
A. R. Kumar ◽  
D.-A. Achimov ◽  
T. Zeng ◽  
G. Chen
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Experimental Study ◽  
Heat Conduction ◽  
Room Temperature ◽  
Conduction Model ◽  
Heat Conduction Model ◽  
Anisotropic Heat Conduction ◽  
3Ω Technique

Abstract We present an experimental study on the thermal conductivity of anodized alumina with regular nanochannels. Thermal conductivity values in both directions parallel and perpendicular to the nanochannel axis are measured at room temperature using the 3ω technique. An anisotropic heat conduction model is developed to analyze the experimental data.

Effects of microstructural evolution on the thermal conductivity of α–Al2O3 prepared from nano-size γ–Al2O3 powder

2000 ◽  
Vol 15 (3) ◽  
pp. 744-750 ◽  
Author(s):  
Eduardo J. Gonzalez ◽  
Grady White ◽  
Lanhua Wei
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Microstructural Evolution ◽  
Vickers Hardness ◽  
Room Temperature ◽  
Volume Fraction ◽  
Al2o3 Powder ◽  
Α Al2o3 ◽  
Thermal Diffusivities ◽  
Nano Size

The thermal diffusivities (D) of porous α–Al2O3 specimens prepared from nano-size γ–Al2O3 powder and from conventional submicrometer-size alumina powders were measured at room temperature, and the thermal conductivity (κ) was calculated from D. Plots of κ versus the volume fraction of porosity (P) showed that the data from both sets of samples followed similar linear curves. Similarly, data of Vickers hardness versus P obtained from the same specimens also followed a single linear curve. The good correlation of thermal diffusivity with P suggests that grain boundaries have a lesser effect on thermal transport than porosity.

Theoretical Conclusions About the Claims of Anomalous Heat Transfer Enhancement Associated With Nanofluids

2013 ◽  
Author(s):  
Wenhao Li ◽  
Chen Yang ◽  
Akira Nakayama
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Free Convection ◽  
Volume Fraction ◽  
Cold Wall ◽  
Nanoparticle Volume Fraction ◽  
Transfer Enhancement ◽  
Anomalous Heat Transfer ◽  
Buongiorno Model ◽  
Anomalous Heat

A theoretical answer to the controversial issue on the anomalous convective heat transfer in nanofluids has been provided, exploiting the Buongiorno model for convective heat transfer in nanofluids with modifications to fully account for the effects of nanoparticle volume fraction distributions on the continuity, momentum and energy equations. Firstly, a set of exact solutions have been obtained for hydrodynamically and thermally fully developed laminar nanofluid forced convection flows in channels and tubes, subject to constant heat flux. From the solutions, it has been concluded that the anomalous heat transfer rate, exceeding the rate expected from the increase in thermal conductivity, is possible in such cases as titania-water nanofluids in a channel, alumina-water nanofluids in a tube and also titania-water nanofluids in a tube. Moreover, the maximum Nusselt number based on the bulk mean nanofluid thermal conductivity is captured when the ratio of Brownian and thermophoretic diffusivities is around 0.5, which can be exploited for designing nanoparticles for high-energy carriers. Secondly, another set of exact solutions have been obtained for free convection in a vertical channel filled with a nanofluid, exploiting the Buongiorno model with nanoparticle volume fraction modifications. The effects of the bulk mean volume fraction of nanoparticles, the ratio of Brownian and thermophoretic diffusivities and the buoyancy ratio on both velocity and temperature profiles has been investigated in depth for the first time. The volume fraction of nanoparticles increases exponentially towards the cold wall, which makes the velocity and temperature gradients steeper near the hot wall than those near the cold wall. Unlike the case of forced convection, no anomalous heat transfer enhancement has been observed in this case of free convection, so that the Nussult number based on the thermal conductivity of nanofluid stays close to unity as in pure base fluid free convection.

scholarly journals Mixed Convection Stagnation Point Flow of the Blood Based Hybrid Nanofluid Around A Rotating Sphere

2020 ◽  
Author(s):  
Taza Gul ◽  
Basit Ali ◽  
Saleem Nasir ◽  
Muhammad Jawad ◽  
Anwar Saeed
Keyword(s):  
Thermal Conductivity ◽  
Heat Transport ◽  
Stagnation Point ◽  
Volume Fraction ◽  
Excellent Result ◽  
Concentration Field ◽  
Hybrid Nanofluid ◽  
Nanoparticle Volume Fraction ◽  
Nanofluid Flow ◽  
Rotating Sphere

Abstract In this new world of fluid technologies, hybrid nanofluid has become a productive subject of research among scientists for its potential thermal features and abilities, which provides an excellent result as compared to nanofluids in growing the rate of heat transport. Our purpose here is to introduce the substantial influences of magnetic field on 2D, time dependent and stagnation point inviscid flow of couple stress hybrid nanofluid around a rotating sphere with base fluid is pure blood, TiO2, and, Ag as the nanoparticles. To translate the governing system of partial differential equations and the boundary conditions relevant for computation, some suitable transformations are implemented. To obtain the analytical estimations for the corresponding system of differential expression, the innovative Homotopy Analysis Method (HAM) approach is used. The characteristics of hybrid nanofluid flow patterns, including temperature, velocity and concentration profiles are simulated and analyzed in detail due to the variation in the evolving variables. A detailed research is also performed in order to investigate the influences of relevant constraints on the rates, momentum and heat transport for both TiO2 + Ag + Blood and TiO2 + Blood. One of the many outcomes of this analysis, it is observed that increasing the magnetic factor will decelerate the hybrid nanofluid flow velocity and improve the temperature profile. It may also be demonstrated that by increasing the Brownian motion factor, significant improvement can be made in the concentration field of hybrid nanofluid. The increase in the nanoparticle volume fraction from 0.01 to 0.02 in case of the hybrid nanofluid enhance the thermal conductivity from 5.8% to 11.947% and for the same value of the nanoparticle volume fraction in case of nanofluid enhance the thermal conductivity from 2.576% to 5.197%.

scholarly journals Unsteady squeezing flow of magnetohydrodynamic carbon nanotube nanofluid in rotating channels with entropy generation and viscous dissipation

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882310 ◽  
Author(s):  
Abdullah Dawar ◽  
Zahir Shah ◽  
Waris Khan ◽  
Muhammad Idrees ◽  
Saeed Islam
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Physical Properties ◽  
Viscous Dissipation ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Rotation Parameter ◽  
Squeezing Flow ◽  
Nanoparticle Volume Fraction

The most favorable gift of modern science is nanofluid. The nanofluid can able to move freely through micro channels with the spreading of nanoparticles. Due to improved convection between the base liquid surfaces and nanoparticles, the nano suspensions express high thermal conductivity. Also, the benefits of suspending nanoparticles in base fluids are increased heat capacity, surface area, effective thermal conductivity, collision, and interaction among particles. This research aim to study squeezing flow of carbon nanotubes based on water (H2O) in rotating channels. Entropy generation is evaluated and for this purpose, second law of thermodynamics is employed. The influences of thermal radiation, viscous dissipation, and applied magnetic field on nanofluid are taken into account. The flow of the nanofluid is considered in unsteady three dimensions. The transformed ordinary differential equations (ODEs) are solved by homotopy analysis method with the help of similarity variables. Results obtained for single and multi-wall carbon nanotubes are compared. Plots have been presented in order to examine how the velocities, temperature, and entropy profiles become affected by numerous physical parameters. Generally, the velocity profiles escalate when the upper plate of the channel moves toward the lower stretching one and reduces when the upper plate is moving away from the lower one. The velocity profile in y-direction escalates with the escalation in nanoparticle volume fraction and suction parameter while the rotation parameter bids dual behavior with the escalating values. The velocity profile in x-direction bids the oscillatory behavior with the enhancement in nanoparticle volume fraction, rotation parameter, and magnetic parameter. The physical properties of carbon nanotubes, thermo physical properties of carbon nanotubes and nanofluid of some base fluids, and thermal conductivity of carbon nanotubes with different volume fractions are shown through tables.

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