Experimental Studies of Thermal Conductivity, Viscosity and Stability of Ethylene Glycol Nanofluids (original) (raw)
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Investigation on Thermal Conductivity, Viscosity and Stability of Nanofluids
2012
In this thesis, two important thermo-physical properties of nanofluids: thermal conductivity and viscosity together with shelf stability of them are investigated. Nanofluids are defined as colloidal suspension of solid particles with the size of lower than 100 nanometer. Thermal conductivity, viscosity and stability of nanofluids were measured by means of TPS method, rotational method and sedimentation balance method, respectively. TPS analyzer and viscometer were calibrated in the early stage and all measured data were in the reasonable range. Effect of some parameters including temperature, concentration, size, shape, alcohol addition and sonication time has been studied on thermal conductivity and viscosity of nanofluids. It has been concluded that increasing temperature, concentration and sonication time can lead to thermal conductivity enhancement while increasing amount of alcohol can decrease thermal conductivity of nanofluids. Generally, tests relating viscosity of nanofluids revealed that increasing concentration increases viscosity; however, increasing other investigated parameters such as temperature, sonication time and amount of alcohol decrease viscosity. In both cases, increasing size of nanofluid results in thermal conductivity and viscosity reduction up to specific size (250 nm) while big particle size (800 nm) increases thermal conductivity and viscosity, drastically. In addition, silver nanofluid with fiber shaped nanoparticles showed higher thermal conductivity and viscosity compared to one with spherical shape nanoparticles. Furthermore, effect of concentration and sonication time have been inspected on stability of nanofluids. Test results indicated that increasing concentration speeds up sedimentation of nanoparticles while bath sonication of nanofluid brings about lower weight for settled particles. Considering relative thermal conductivity to relative viscosity of some nanofluids exposes that ascending or descending behavior of graph can result in some preliminary evaluation regarding applicability of nanofluids as coolant. It can be stated that ascending trend shows better applicability of the sample in higher temperatures while it is opposite for descending trend. Meanwhile, it can be declared that higher value for this factor shows more applicable nanofluid with higher thermal conductivity and less viscosity. Finally, it has been shown that sedimentation causes reduction of thermal conductivity as well as viscosity. For further research activities, it would be suggested to focus more on microscopic investigation regarding behavior of nanofluids besides macroscopic study. IV Acknowledgment There are so many people that we would like to thank due to their support, encouragement, and assistance. Firstly, we should sincerely express our great gratitude to Professor Björn Palm for his enormous patience, sophisticated comments, consistent support, and make the possibility for us to work at ETT laboratory of Energy Department of KTH and acquire very nice experiences. We would also like to thank Dr. Rahmatollah Khodabandeh due to his support and kindness during our thesis work. Very special thanks go to Ehsan Bitaraf Haghighi who played a significant role in our thesis work and opened doors of nanotechnology science for us. He was not only an excellent supervisor with great energy all day long, but also a very gentle friend. Ehsan, without your support and constructive suggestions it was impossible for us to end up with this much work.
Enhanced thermal conductivity and viscosity of copper nanoparticles in ethylene glycol nanofluid
Journal of Applied Physics, 2008
This study investigates the thermal conductivity and viscosity of copper nanoparticles in ethylene glycol. The nanofluid was prepared by synthesizing copper nanoparticles using a chemical reduction method, with water as the solvent, and then dispersing them in ethylene glycol using a sonicator. Volume loadings of up to 2% were prepared. The measured increase in thermal conductivity was twice the value predicted by the Maxwell effective medium theory. The increase in viscosity was about four times of that predicted by the Einstein law of viscosity. Analytical calculations suggest that this nanofluid would not be beneficial as a coolant in heat exchangers without changing the tube diameter. However, increasing the tube diameter to exploit the increased thermal conductivity of the nanofluid can lead to better thermal performance.
Colloid & Nanoscience Journal
Thermal conductivity and viscosity of CuO/ethylene glycol/water, multiwalled carbon nanotubes (MWCNT)/ethylene glycol/water and CuO/MWCNT/ethylene glycol/water nanofluid systems were determined experimentally at a temperature range of 5 to 50 °C and very low concentration (less than 0.008 vol.%). The obtained results show that the thermal conductivity of nanofluids significantly increases with increasing nanofluid temperature. It is also verified that the enhancement in thermal conductivity of nanofluid systems containing mixed CuO/MWCNT is more than systems containing CuO or MWCNT individually. Analyses of the viscosity data indicate that the viscosity diminishes with increasing temperature. The higher concentrations of all nanofluid systems possess higher viscosity. The results also show that the viscosity of nanofluid systems containing mixed CuO/MWCNT is between the viscosities of the systems containing CuO and MWCNT individually.
Investigation of Viscosity and Rheological Properties of Copper/Ethylene Glycol Nanofluid
Challenges in Nano and Micro Scale Science and Technology, 2021
In recent years, significant attention has been devoted to nanofluids to improve the thermal efficiency of conventional cooling fluids. Copper nanoparticles are a proper candidate for this purpose due to their high thermal conductivity. In this study, stable copper nanoparticles with a 34.5 nm average diameter were synthesized via chemical reduction without an inert environment. The synthesized copper nanoparticles and also commercial copper nanoparticles with a 40 nm average size were used in ethylene glycol as the base fluid. Viscosity and rheological behavior of these nanofluids as important factors for assessment of flow behavior in heat exchange equipment were also investigated experimentally. The effects of volume fraction and temperature on nanofluid viscosity were investigated. Viscosity was measured in a 29.5-60 °C temperature range at low weight fractions of 0.0001, 0.0003, and 0.0005. The results were compared with the proposed models for the prediction of nanofluid viscosity, suggesting a correlation. The results show the Newtonian behavior of both nanofluids. Based on the results of a previous study, the heat transfer coefficient and thermal conductivity increased significantly (38.2 % for 0.03 wt. % nanofluid at Re=68 and 39.4% for 0.01 wt. %, respectively). Also, for both cases, nanofluid viscosity was smaller than the base fluid (for nanofluid B, 12.8% reduction at 1.06 vol. %). These results suggest copper nanofluid as an appropriate alternative for application in heat exchange equipment.
A colloidal mixture of nano-sized (<100 nm) particles in a base liquid called nanofluid, which is the new generation of heat transfer fluid for various heat transfer applications where transport characteristics are substantially higher than the base liquid. In the present study, the effects due to temperature and concentration on thermophysical properties (thermal conductivity, viscosity and density) for Al 2 O 3 /water/ethylene glycol based nanofluids are experimentally investigated. The volume fractions of nanoparticles used were 0.1%, 0.25%, 0.50% and 1.0%. The present work focuses on thermal conductivity and viscosity measurement of fluid mixture. This however, has not been addressed properly so far. Results show that thermal conductivity increases with nanoparticles concentration as well as with the temperature. Whereas, viscosity and density decreases with temperature and increases with nanoparticles concentration.
A Comprehensive Review on Thermal Conductivity and Viscosity of Nanofluids
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2022
The innovation of nanofluids, a novel working fluid, has presented the development of heat transfer properties in machining, automotive engine cooling systems, pumping power and others to optimize the overall system. Nanofluids have pulled in scientists' cogitation from various fields in designing new thermal systems for different engineering applications due to their distinctive thermophysical properties and prospective applications. Long term stability, improved thermal conductivity, and viscosity are the principal fundamental expectations in nanofluids research to achieve better heat transfer performance. In the previous couple of decades, various investigations have been completed to explore the nanofluids properties augmentation. For instance, kerosene-based oleic acid-coated Fe3O4 nanofluids showed 300% improvement of thermal conductivity, and water-based single-walled carbon nanotube revealed 320% improvement of viscosity. This paper presents a survey of recent exploratio...
International Journal of Heat and Mass Transfer, 2017
Experimental study has been carried out to determine the thermal conductivity of five different nanofluids containing aluminum oxide, copper oxide, zinc oxide, silicon dioxide and titanium dioxide nanoparticles dispersed in a base fluid of 60:40 (by mass) propylene glycol and water mixture. The effect of particle volumetric concentration up to 6% was studied with temperatures ranging from À30°to 90°C. Experiments showed an increase in thermal conductivity of nanofluids with increasing concentration and temperature. The thermal conductivity of nanofluids showed a strong dependence on particle volumetric concentration, particle size, properties of particles and the base fluid and temperature. Several existing theoretical models for thermal conductivity of nanofluids were compared with the experimental data, but they all showed disagreement. From comparisons, the most agreeable model was selected and a curve-fit constant was derived to match the data of propylene glycol nanofluids. This model expresses the thermal conductivity of nanofluids as a function of Brownian motion, Biot number, fluid temperature, particle volumetric concentration, and the properties of the nanoparticles and the base fluid. This model provided good agreement with 600 experimental data points obtained from five different nanofluids with an average absolute deviation of 1.79 percent. Because of the enhanced thermal conductivity with increasing temperature, nanofluids should be more beneficial at higher temperature applications.
Applied Physics Letters, 2001
It is shown that a ''nanofluid'' consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter Ͻ10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.
International Communications in Heat and Mass Transfer, 2012
In this paper the effect of CuO nanoparticles on the thermal conductivity of base fluids like mono ethylene glycol and water was studied. Both the base fluids showed enhancement in effective thermal conductivity. This enhancement was investigated with regard to various factors; concentration of nanoparticles, types of base fluids, sonication time and settlement time. For both the base fluids, an improvement in thermal conductivity was found as concentration of nanoparticles increased due to interaction between particles. It was also found that as the sonication time was increased, there was furthermore an improvement in the thermal conductivity of the base fluids. Effect of base fluids is the complex idea to understand. Lower base fluid's viscosities are supposed to contribute grater enchantment, but another factor of fluid nanoparticles surface interaction also more important. The experimentally measured thermal conductivities of base fluid's nanoparticles suspension were compared to a variety of models (Maxwell, Hamilton-Crosser and Bruggeman Model). It is observed that none of the mentioned models were found to predict accurately the thermal conductivities of nanofluids.
To get more experimental and fundamental understanding of the thermal behavior of nanofluids, the thermal conductivity of Al2O3–EG nanofluids have been examined using a KD2-Pro thermal analyzer. The effects of temperature and concentration on thermal conductivity of nanofluid are investigated. The experiments performed at temperature ranging from 24 C to 50 C while volume fractions up to 5%. The experimental results exhibited that the thermal conductivity of nanofluids enhances significantly with increase in concentration and temperature. Also, attempts were made to propose new accurate correlations for estimating thermal conductivity at different temperatures and concentrations. For this purpose, two new correlations with very high accuracy were suggested. To estimate thermal conductivity at different temperatures, focusing more on accuracy and usability, several correlations have been proposed. These correlations have been presented separately at different temperatures which can be more accurate.