scholarly journals Preparation and Enhancement of Thermal Conductivity of Heat Transfer Oil-Based MoS2Nanofluids

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yuan-Xian Zeng ◽  
Xiu-Wen Zhong ◽  
Zhao-Qing Liu ◽  
Shuang Chen ◽  
Nan Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Surface Modification ◽  
Stearic Acid ◽  
Mass Fraction ◽  
Laser Flash ◽  
Thermal Conductivity Enhancement ◽  
Flash Method ◽  
Conductivity Enhancement ◽  
Increasing Temperature

The lipophilic MoS2nanoparticles are synthesized by surface modification with stearic acid (SA). The heat transfer oil-based nanofluids, with the mass fraction of lipophilic nanoparticles varying from 0.25% up to 1.0%, are prepared and their thermal conductivity is determined at temperatures ranging from 40 to 200°C using an apparatus based on the laser flash method. It has been found that the nanofluids have higher thermal conductivity and the thermal conductivity enhancement increased not only with increasing mass fraction of nanoparticles, but also with increasing temperature in the range 40–180°C The results show a 38.7% enhancement of the thermal conductivity of MoS2nanofluid with only 1.0% mass fraction at 180°C.

scholarly journals Thermal Conductivity of Ionic Liquids and IoNanofluids. Can Molecular Theory Help?

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 116
Author(s):  
Xavier Paredes ◽  
Maria José Lourenço ◽  
Carlos Nieto de Castro ◽  
William Wakeham
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ionic Liquids ◽  
Imaging Techniques ◽  
Interfacial Area ◽  
Thermal Conductivity Enhancement ◽  
Molecular Theory ◽  
Estimation Methods ◽  
Diphenyl Oxide ◽  
Conductivity Enhancement

Ionic liquids have been suggested as new engineering fluids, specifically in the area of heat transfer, and as alternatives to current biphenyl and diphenyl oxide, alkylated aromatics and dimethyl polysiloxane oils, which degrade above 200 °C, posing some environmental problems. Addition of nanoparticles to produce stable dispersions/gels of ionic liquids has proved to increase the thermal conductivity of the base ionic liquid, potentially contributing to better efficiency of heat transfer fluids. It is the purpose of this paper to analyze the prediction and estimation of the thermal conductivity of ionic liquids and IoNanofluids as a function of temperature, using the molecular theory of Bridgman and estimation methods previously developed for the base fluid. In addition, we consider methods that emphasize the importance of the interfacial area IL-NM in modelling the thermal conductivity enhancement. Results obtained show that it is not currently possible to predict or estimate the thermal conductivity of ionic liquids with an uncertainty commensurate with the best experimental values. The models of Maxwell and Hamilton are not capable of estimating the thermal conductivity enhancement of IoNanofluids, and it is clear that the Murshed, Leong and Yang model is not practical, if no additional information, either using imaging techniques at nanoscale or molecular dynamics simulations, is available.

scholarly journals The difference in the thermal conductivity of nanofluids measured by different methods and its rationalization

2016 ◽  
Vol 7 ◽  
pp. 2037-2044 ◽  
Author(s):  
Aparna Zagabathuni ◽  
Sudipto Ghosh ◽  
Shyamal Kumar Pabi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Laser Flash ◽  
Flash Method ◽  
Transfer Model ◽  
Measuring Methods ◽  
Order Of Magnitude ◽  
Wire Method ◽  
The Difference ◽  
First Time

A suspension of particles below 100 nm in size, usually termed as nanofluid, often shows a notable enhancement in thermal conductivity, when measured by the transient hot-wire method. In contrast, when the conductivity of the same nanofluid is measured by the laser flash method, the enhancement reported is about one order of magnitude lower. This difference has been quantitatively resolved for the first time on the basis of the collision-mediated heat transfer model for nanofluids proposed earlier by our research group. Based on the continuum simulation coupled with stochastic analysis, the present theoretical prediction agrees well with the experimental observations from different measuring methods reported in the literature, and fully accounts for the different results from the two measuring methods mentioned above. This analysis also gives an indication that the nanofluids are unlikely to be effective for heat transfer in microchannels.

Thermoelectric Properties of Hot-Pressed GaN and InN

2003 ◽  
Vol 793 ◽  
Author(s):  
A. Yamamoto ◽  
S. Yamaguchi
Keyword(s):  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Laser Flash ◽  
Flash Method ◽  
Nitride Semiconductors ◽  
Hot Press ◽  
Press Method ◽  
Increasing Temperature

ABSTRACTAn attempt was made to obtain bulk III-nitride semiconductors such as InN, GaN and InxGa1−xN alloy using hot-press method in order to test their high temperature thermoelectric properties. The Seebeck coefficient and the resistivity were –10μV/K and 1.8×10−6Ωm for InN, and –50μV/K and 1.9×10−4Ωm for GaN at 300K, respectively. Thermal conductivity determined by laser flash method with porosity correction was 17W/mK for InN and 2.6W/mK for GaN. For InN the Seebeck coefficient and the resistivity increased monotonously with increasing temperature, which indicates that InN is a metal or a degenerately doped semiconductor. The power factor and the figure of merit were 2.1 × 10−4W/mK2and 1.5×10−5K−1for InN and 6.9 × 10−5W/mK2and 2.6×10−5K−1for GaN at 650K, respectively.

Thermal Conductivity Enhancement of Aluminium Oxide Nanofluid in Ethylene Glycol

2014 ◽  
Vol 660 ◽  
pp. 730-734 ◽  
Author(s):  
Khamisah Abdul Hamid ◽  
Wan Hamzah Azmi ◽  
Rizalman Mamat ◽  
Nur Ashikin Usri
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Ethylene Glycol ◽  
Volume Concentration ◽  
Conductivity Measurement ◽  
Thermal Conductivity Enhancement ◽  
Heat Transfer Fluid ◽  
Coolant Fluid ◽  
Conductivity Enhancement

Nanofluids are the new coolant fluid that has been widely investigates due to its ability to improved heat transfer better than conventional heat transfer fluid. The need to study the nanofluid properties has been increased to provide better understanding on nanofluid thermal properties and behavior. This study presents the measurement analysis on thermal conductivity enhancement of Al2O3 nanoparticles dispersed in ethylene glycol. The nanofluids are prepared using two step method for volume concentration range from 1.0 % to 4.0 %. The thermal conductivity measurement of the nanofluid is performed by KD2 Pro Thermal Properties Analyzer at working temperature range from 30 °C to 80 °C. The maximum enhancement in thermal conductivity is 21.1 % at volume concentration of 2.0 % and temperature of 70 °C. The results show that the thermal conductivity increases with the increase of nanofluid concentration and temperature. Also, the nanofluid shows enhancement in thermal conductivity compare to the base fluid.

Recent Development in the Investigation on Thermal Conductivity of Silicate Melts

2012 ◽  
Vol 31 (4-5) ◽  
pp. 491-499 ◽  
Author(s):  
Hiroki Hasegawa ◽  
Hiromichi Ohta ◽  
Hiroyuki Shibata ◽  
Yoshio Waseda
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Chemical Composition ◽  
Laser Flash ◽  
Laser Flash Method ◽  
Silicate Melts ◽  
Flash Method ◽  
Bottom Surface ◽  
High Time Resolution

AbstractAccurate values of thermal conductivity of the silicate melts systematically measured as a function of chemical composition are necessary to understand a mechanism of heat transfer in the silicate melts. Hot wire method and laser flash methods have been used to measure thermal conductivity or thermal diffusivity of oxides melts at high temperatures. Laser flash method has been improved to measure thermal diffusivity of oxides melts with high accuracy. However the effects of radiative heat transfer and low electrical resistivity of samples have been made it difficult to derive precise values. To overcome these difficulties, a front-heating front-detection laser flash method with use of high time resolution detector has been proposed. The temperature response at the bottom surface of thin platinum cell containing sample irradiated by pulse laser is measured. The measurement techniques used for measurement oxide melts are compared. Then, thermal conductivity of Al2O3-Na2O-CaO-SiO2 silicate melts was measured at temperature up to 1830 K. Thermal conductivity of the molten silicate shows insignificant temperature dependence for all investigated melts. A fairly good correlation has been found between the thermal conductivity and the value of NBO/T (Non-Bridging Oxygen ions/Tetrahedrally coordinated cation) calculated from the chemical composition. The thermal conductivity increases with decrease of NBO/T for small NBO/T value and becomes constant for larger NBO/T value.

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