Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

2001 ◽  
Vol 78 (6) ◽  
pp. 718-720 ◽  
Author(s):  
J. A. Eastman ◽  
S. U. S. Choi ◽  
S. Li ◽  
W. Yu ◽  
L. J. Thompson
Keyword(s):  
Ethylene Glycol ◽  
Copper Nanoparticles ◽  
Thermal Conductivities

A Facile Route to Prepare Hydrophilic Copper Nanoparticles and their Thermal Conductivities

2011 ◽  
Vol 279 ◽  
pp. 136-141
Author(s):  
Dan Li
Keyword(s):  
Thermal Conductivity ◽  
Copper Nanoparticles ◽  
Coating Layer ◽  
Organic Media ◽  
Organometallic Precursor ◽  
Facile Route ◽  
Thermal Conductivities

Well-dispersed and hydrophilic copper nanoparticles have been synthesized from an organometallic precursor in an organic (or oil) phase. There are two layers coated on the surface of the copper nanoparticles. The coating layer can not be dissolved or rinsed off by organic media. The changing of viscosity and enhancement of the thermal conductivity of copper nanofluids is also presented.

The Preparation and Thermal Conductivities Enhacement of Nanofluids Containing Graphene Oxide Nanosheets

2010 ◽  
Author(s):  
Wei Yu ◽  
Huaqing Xie ◽  
Lifei Chen ◽  
Yang Li ◽  
Dehui Li
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Ethylene Glycol ◽  
High Stability ◽  
Hot Wire ◽  
Graphene Oxide Nanosheets ◽  
Metallic Oxide ◽  
Conductivity Enhancement ◽  
Hydrophilic Surfaces ◽  
Thermal Conductivities

The work presents a method to prepare stable nanofluids containing graphene oxide nanosheets (GO-EG nanofluid). The hydrophilic surfaces let graphene oxide nanosheets have good compatibility with ethylene glycol. The thermal conductivity of the nanofluids was measured by a short hot wire technique, and the result shows that the thermal conductivity of GO-EG nanofluids is almost constant within 7 days, and it reflects the high stability of GO-EG nanofluids. The thermal conductivity enhancement ratios of GO-EG nanofluids were almost constant with tested temperatures vary. GO-EG nanofluids have substantially higher thermal conductivities than the base fluids. When the loading is 5.0 vol.%, the enhancement ratios is up to 61%, much larger than those of metallic oxide. For 1.0 vol.% GO-EG nanofluid, the enhancement ratios is 10.5%, less than those of CNT with the same loading. The reason may be due to the defects, caused by the treatment with strong Oxidants. In our opinion, heat transport in the GO nanosheet is one of the major contributions to the increase of the effective thermal conductivity of nanofluids.

scholarly journals Effect of Copper Nanoparticles Dispersion on Catalytic Performance of Cu/SiO2Catalyst for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yajing Zhang ◽  
Na Zheng ◽  
Kangjun Wang ◽  
Sujuan Zhang ◽  
Jing Wu
Keyword(s):  
Ethylene Glycol ◽  
Copper Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Bet Surface Area ◽  
X Ray ◽  
Dimethyl Oxalate ◽  
Effect Of Copper ◽  
Average Size

Cu/SiO2catalysts, for the synthesis of ethylene glycol (EG) from hydrogenation of dimethyl oxalate (DMO), were prepared by ammonia-evaporation and sol-gel methods, respectively. The structure, size of copper nanoparticles, copper dispersion, and the surface chemical states were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) and N2adsorption. It is found the structures and catalytic performances of the catalysts were highly affected by the preparation method. The catalyst prepared by sol-gel method had smaller average size of copper nanoparticles (about 3-4 nm), better copper dispersion, higher Cu+/C0ratio and larger BET surface area, and higher DMO conversion and EG selectivity under the optimized reaction conditions.

The Synthesis and Characterizations of Narrow-Dispersed Copper Nanoparticles

2009 ◽  
Author(s):  
Wei Yu ◽  
Huaqing Xie ◽  
Lifei Chen ◽  
Yang Li ◽  
Chen Zhang
Keyword(s):  
Ethylene Glycol ◽  
Copper Nanoparticles ◽  
Pure Copper ◽  
Synthesis Method ◽  
Reaction Medium ◽  
Polyvinyl Pyrrolidone ◽  
Copper Particles ◽  
Reduction Property ◽  
Pure Phase ◽  
The Mean

A controlled synthesis method for preparing narrow-dispersed copper nanoparticles, using water and ethylene glycol as the reaction mediums respectively, has been reported. In order to obtain pure-phase copper nanoparticles using water, the reaction time of 8h is essential. Owing to the reduction property of ethylene glycol, the reaction rate using ethylene glycol is higher. In addition, the amount of reduction agent can reduce largely. Polyvinyl pyrrolidone plays great role on the size of copper particles, and the increasing of polyvinyl pyrrolidone concentration attributes to the smaller dimension particles. The mean diameter is about 4 nm when the concentration of polyvinyl pyrrolidone is 0.5 mmol/L. Polyvinyl pyrrolidone acts as the polymeric capping agents in the reaction, preventing the agglomeration of the copper nanoparticles. When water is the reaction medium, Cu2+ complex is reduced to Cu+ complex firstly, and the further reduction of Cu+ forms the pure copper nanoparticle.

Equilibrium Molecular Dynamics Simulation Study on the Effect of Nanoparticle Loading and Size on Thermal Conductivity of Nanofluids

2007 ◽  
Author(s):  
R. Panneer Selvam ◽  
Suranjan Sarkar
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Copper Nanoparticles ◽  
Thermal Conduction ◽  
Base Fluid ◽  
Liquid Argon ◽  
Dynamics Simulation ◽  
Solid Copper ◽  
Thermal Conductivities

Nanofluids have been proposed as a route for surpassing the performance of currently available heat transfer liquids for better thermal management needed in many diverse industries and research laboratories. Recent experiments on nanofluids have indicated a significant increase in thermal conductivity with 0.5 to 2% of nanoparticle loading in comparison to that of the base fluid. But the extent of thermal conductivity enhancement sometimes greatly exceeds the predictions of well established classical theories like Maxwell and Hamilton Crosser theory. In addition to that, these classical theories can not explain the temperature and nanoparticle size dependency of nanofluid thermal conductivity. Atomistic simulation like molecular dynamics simulation can be a very helpful tool to model the enhanced nanoscale thermal conduction and predict thermal conductivities in different situations. In this study a model nanofluid system of copper nanoparticles in argon base fluid is successfully modeled by equilibrium molecular dynamics simulation in NVT ensemble and thermal conductivities of base fluid and nanofluids are computed using Green Kubo method. The interatomic interactions between solid copper nanoparticles, base liquid argon atoms and between solid copper and liquid argon are modeled by Lennard Jones potential with appropriate parameters. For different volume fractions of nanoparticle loading, the thermal conductivities are calculated. The nanoparticle size effects on thermal conductivities of nanofluids are also systematically studied. This study indicates the usefulness of MD simulation to calculate thermal conductivity of nanofluid and explore the higher thermal conduction in molecular level.

Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid

2008 ◽  
Vol 103 (7) ◽  
pp. 074301 ◽  
Author(s):  
J. Garg ◽  
B. Poudel ◽  
M. Chiesa ◽  
J. B. Gordon ◽  
J. J. Ma ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Copper Nanoparticles ◽  
Enhanced Thermal Conductivity

The Role of Liquid Layering on the Enhancement of Thermal Conductivity in Nanofluids

2010 ◽  
Author(s):  
M. Reza Azizian ◽  
Elham Doroodchi ◽  
Behdad Moghtaderi
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Simple Model ◽  
Ethylene Glycol ◽  
Copper Oxide ◽  
Maxwell Theory ◽  
New Model ◽  
Liquid Layering ◽  
Thermal Conductivities

Liquid layering is considered to be one of the key mechanisms responsible for the remarkably high thermal conductivities exhibited by nanofluids. A number of models have been presented in recent years to quantify the effect of liquid layering. However, many of these models are either based on unrealistic assumptions or have been incorrectly formulated. In this study we propose a new, yet simple, model that resolves the shortcomings of earlier models. The new model is based on the Maxwell theory and takes into account the effect of nanolayering. The model was compared with several sets of experimental data on Copper Oxide-in-ethylene glycol, Copper Oxide-in-water, Alumina-in-water, and Gold-in-toluene. The results indicate that the contribution of nanolayering to the enhancement of thermal conductivity in nanofluids is relatively modest and as such cannot be solely responsible for the observed enhancements.

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