scholarly journals Study of Ultrasonic Attenuation and Thermal Conduction in Bimetallic Au/Pt Nanofluids

2020 ◽  
Author(s):  
Alok Kumar Verma ◽  
Navneet Yadav ◽  
Shakti Pratap Singh ◽  
Kajal Kumar Dey ◽  
Devraj Singh ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Conduction ◽  
Base Fluid ◽  
Ultrasonic Attenuation ◽  
Thermal Constant ◽  
Absorption Feature ◽  
Two Phase ◽  
Mechanistic Approach ◽  
Hot Disk

Here, we report the frequency dependent ultrasonic attenuation of monometallic Au and bimetallic Au/Pt based aqueous nanofluids (NFs). The as synthesized bimetallic nanofluids (BMNFs) revealed less resistance to ultrasonic wave compared to the monoatomic NFs. Thermal conductivity of both nanofluids taken at different concentrations, measured by the Hot Disk Thermal Constant Analyzer (TPS-500) revealed substantial conductivity improvement when compared to the base fluid, although Au/Pt showed lesser improvement compared to Au. We rationalized our obtained results with thorough characterization of the as synthesized nanoparticles/fluids with techniques such as XRD, UV-Vis, TEM, EDS etc. and some of the important information revealed were about the distinct two-phase bimetallic nature of Au/Pt, its two plasmonic band optical absorption feature and the spherical morphology of the particles. The findings were correlated with the observed thermal and ultrasonic behaviour and proper rationalization was provided. It was revealed that the comparatively lesser thermal conductivity of Au/Pt had direct implication on its attenuation property. The findings could have important repercussions in both industrial applicational aspects and mechanistic approach towards the field of ultrasonic attenuation in nanofluids

scholarly journals The Classical Nature of Thermal Conduction in Nanofluids

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Jacob Eapen ◽  
Roberto Rusconi ◽  
Roberto Piazza ◽  
Sidney Yip
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Strong Evidence ◽  
Thermal Conduction ◽  
Base Fluid ◽  
Liquid Mixtures ◽  
Large Set ◽  
Conductivity Data ◽  
Homogeneous Systems ◽  
Thermal Conductivity Data

We show that a large set of nanofluid thermal conductivity data falls within the upper and lower Maxwell bounds for homogeneous systems. This indicates that the thermal conductivity of nanofluids is largely dependent on whether the nanoparticles stay dispersed in the base fluid, form large aggregates, or assume a percolating fractal configuration. The experimental data, which are strikingly analogous to those in most solid composites and liquid mixtures, provide strong evidence for the classical nature of thermal conduction in nanofluids.

Effect of Different Firing Temperature on Thermal Conductivity of Ceramic Tiles

2020 ◽  
Vol 1010 ◽  
pp. 665-671
Author(s):  
Khairul Anuar Shariff ◽  
Muhammad Syahir Juhari ◽  
Lynette Wei Ling Chan ◽  
Shah Rizal Kasim
Keyword(s):  
Thermal Conductivity ◽  
Firing Temperature ◽  
The Body ◽  
Thermal Constant ◽  
High Porosity ◽  
Ceramic Tiles ◽  
Tile Body ◽  
Trapped Air ◽  
Hot Disk ◽  
Body Formulation

The aim of this study is to investigate the effect of different firing temperature on thermal conductivity of ceramic tiles. The body formulation powders of ceramic tiles were made according to the formulation given by company and compacted at 18 MPa using pressing machine in order to obtain button shape specimen with 50 mm diameter. The button shape specimen was fired at different firing temperature which 1150°C, 1175°C, 1200°C and 1225°C. Then, the thermal conductivity of fired specimens was measured by using Hot-Disk Thermal Constant Analyzer. Thermal conductivity result shows that the ceramic tile body fired at 1150 °C producing the lowest thermal conductivity values (0.97 W/mK) in comparison with other specimens. This low thermal conductivity performance is due to the high porosity value in the specimen as a result of more trapped air and implies delaying the heat transfer either inward or outward from the ceramic tiles. Therefore, this study proved that by altering firing temperature, different thermal conductivity values of ceramic tiles were obtained.

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.

Thermophysical Properties of Two-Phase Refrigerant Based Nanofluids in a Refrigeration Cycle

2016 ◽  
Author(s):  
Bilgehan Tekin ◽  
Almila G. Yazicioglu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermophysical Properties ◽  
Base Fluid ◽  
Two Phase Flow ◽  
Cooling System ◽  
Heat Transfer Analysis ◽  
Refrigeration Cycle ◽  
Phase Flow ◽  
Two Phase

Nanofluids are a class of fluids with nanoparticles suspended in a base fluid. The aim for using nanofluids is often to improve the thermophysical properties of the base fluid so as to enhance the energy transfer efficiency. As the technology develops; the size of devices and systems needs to get smaller to fulfill the engineering requirements and/or to be leading among competitors. The use of nanofluids in heat transfer applications seems to be a viable solution to current heat transfer problems, albeit with certain limitations. As an enhancing factor for the thermal conductivity of the base fluid, nanofluids are considered to be use in cooling system applications. For these applications, the base fluid, the refrigerant, exists as a two-phase liquid-vapor mixture in parts of the refrigeration cycle. To analyze, design and optimize the cycle in such applications, the thermophysical properties of the refrigerant based nanofluids for two-phase flow of refrigerant are needed. There are different models present in the literature derived for the thermophysical properties of nanofluids. However, a majority of the existing models for nanofluid thermophysical properties have been proposed for water- and other liquids-based nanofluids, through theoretical, numerical and experimental research. Therefore, the existing models for determination of the nanofluid thermophysical properties are not applicable for refrigerant based nanofluid applications when the results are compared. Thus, in this work, a new model is derived for the thermal conductivity and viscosity of refrigerant based nanofluids, using existing data from both heat transfer and thermophysical property measurement experiments. The effect of the nanoparticles on heat transfer in two phase flow of the refrigerant is considered by applying the two phase heat transfer correlations in the literature to experimental data. As a result, the thermophysical properties of the known states are determined through known heat transfer performance. Even though the model is developed from the analysis of flow in an evaporator and flow in a single tube with evaporating refrigerant, it is aimed to cover the flows in both evaporator and condenser sections in a vapor compression refrigeration cycle to provide the necessary models for thermophysical properties in heat transfer devices which will allow the design of both cycle and evaporator or condenser in terms of sizing and rating problems by performing heat transfer analysis and/or optimization. The model can also be improved by considering the effects of slip mechanisms that lead to slip velocity between the nanoparticle and base fluid.

scholarly journals Production and Thermal Characterization of Ethanol Blends from Black Jaggery

2020 ◽  
Vol 8 (6) ◽  
pp. 5398-5401
Keyword(s):  
Thermal Conductivity ◽  
Global Warming ◽  
Thermal Properties ◽  
Fossil Fuels ◽  
Fossil Fuel ◽  
Thermal Characterization ◽  
Thermal Constant ◽  
Ethanol Blends ◽  
Alternate Fuels

To protect the environment from the global warming dependency on the fossil fuels have to be reduced. Locally available alternate fuels are greatly prominent for the development of industrialization compared to conventional fuels. This paper mainly deals with the production of Ethanol from a source called “Black Jaggery” and an Optimization of the extracted alcohol to attain the characteristics and properties which would be essential to blend the alcohol with an existing fossil fuel. Black Jaggery being a sugar-based product is fermented in the presence of a yeast enzyme for several days and is distilled to extract the bio-fuel (ethanol) from the source. The extracted oil is characterized for the thermal properties by using thermal constant analyzer TPS-500 which will be helpful for the combustion studies. Obtained results shows that compared to E-5, E-10 and E-20, E-15 blend shows better thermal properties increased thermal conductivity, thermal diffusivity with reduced specific heat.

Characterization of Electrokinetic Properties of Nanofluids

2008 ◽  
Vol 8 (11) ◽  
pp. 5966-5971 ◽  
Author(s):  
S. M. Sohel Murshed ◽  
Kai Choong Leong ◽  
Chun Yang
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Electrolyte Concentration ◽  
Ph Value ◽  
Deionized Water ◽  
Hydrodynamic Diameter ◽  
Volume Percentage ◽  
Effects Of Ph

The effects of pH value, surfactant, and electrolyte concentration on zeta potential, particle agglomeration, and thermal conductivity of nanofluids are investigated. The zeta potential of TiO2 (15 nm) nanoparticles in deionized water of different pH values was measured and the iso-electric point was found to be between 4.9 and 5.2. Addition of surfactant in the base fluid increases the zeta potential and thus increases the effective thermal conductivity of nanofluids. The results show that the higher the electrolyte concentration, the smaller the particle zeta potential, which results in increased agglomeration of particles. The enhanced thermal conductivity of TiO2/deionized water-based nanofluids was found to decrease with increasing pH value or electrolyte concentration. At 0.2 volume percentage of TiO2 nanoparticles, the decrease of thermal conductivity of nanofluids was within 2% when the pH value or electrolyte concentration was increased from 3.4 to 9 or 0.01 mM to 10 mM, respectively. The hydrodynamic diameter of agglomerated nanoparticles in base fluid was also measured and found to increase with increasing electrolyte concentration.

Preparation and Characterisation of Graphene Nanofluid: To Be Used As Coolant

2020 ◽  
Author(s):  
Senthil Kumar Velukkudi Santhanam ◽  
Dolly Austen Thomas ◽  
Mystica Augustine Michael Duke ◽  
Viswanathan Doraiswamy
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Base Fluid ◽  
Solid Phase ◽  
Nano Particles ◽  
Planar Geometry ◽  
Phase System ◽  
Transfer Coefficients ◽  
Two Phase ◽  
The Stability

Abstract In the recent years, nanofluids embarked as a new class of fluids with improved thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients thus promoting better heat transfer. Nanofluids consists of two-phase system where the nano sized solid phase (nanoparticles) is dispersed into a base fluid. Graphene is a material which has two-dimensional planar geometry with thermal conductivity of the order of 5000 W/mK. Nanoparticles in the form of thin flakes as small as 50 nm, 100 nm has been used in this study. Two step technique is the used method for preparing nanofluids. Inclusion of additives in small quantity, enhance the durability of the nano particles inside the conventional base fluids. The stability of the solid nano particles inside the conventional base fluid is increased by using surfactants. The heat transfer capacity and stability of the fluids are considered as the basic properties for investigation. The nanofluids characterization studies were drawn from the SEM, XRD and thermal conductivity results. Hot wire method was used to determine the thermal conductivity of the nanofluids. The preparation and properties of graphene based nanofluids which can be used as coolant are studied in this work.

Assessment of hydrothermal performance by thermophysical characterization of a crimped glass wool building insulation

2016 ◽  
Vol 40 (5) ◽  
pp. 401-416 ◽  
Author(s):  
Laurent Marmoret
Keyword(s):  
Thermal Conductivity ◽  
Thermal Characterization ◽  
World Market ◽  
Glass Wool ◽  
Hot Disk ◽  
And Performance ◽  
Phase Water ◽  
Low Sensitivity ◽  
Thermophysical Characterization

There is a need for experimental determination of thermophysical properties to bridge the gap between theoretically prediction and performance of insulating materials in buildings. This investigation concerns the study of hydrothermal performance of glass wool, a widely used insulation on the world market. It has been shown the low sensitivity of glass wool to water vapor, low hygroscopicity, and low permeability. On the other hand, the liquid permeability of glass wool is important. Obviously, the presence of liquid is generally accidental and should be prevented by good workmanship. Thermal characterization (conductivity and diffusivity) by hot disk, a transient technique, has been determined as a function of water. The effect of vapor phase water on thermal properties is not significant. Thermal conductivity increases by a factor 2 when liquid water is present in the insulation. It is shown that the hot disk method is useful to determine thermal characterization of insulation materials. Variations of thermal conductivity with water content have been explained from hydric characterization.

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