Investigation on Convective Heat Transfer and Flow Features of Nanofluids
01 Feb 2003-Journal of Heat Transfer-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 125, Iss: 1, pp 151-155
TL;DR: In this article, an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat-transfer fluids, which are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluid, and they represent the best hope for enhancing heat transfer.
Abstract: Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in many industrial applications. In this paper we propose that an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids. The resulting {open_quotes}nanofluids{close_quotes} are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluids, and they represent the best hope for enhancement of heat transfer. The results of a theoretical study of the thermal conductivity of nanofluids with copper nanophase materials are presented, the potential benefits of the fluids are estimated, and it is shown that one of the benefits of nanofluids will be dramatic reductions in heat exchanger pumping power.
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TL;DR: In this article, a numerical evaluation of three oxide-based nanofluids and their hybrids is proposed, which is a function of the Reynolds number, Prandtl number, and nanoparticle concentration.
180 citations
TL;DR: In this paper, the effects of convective heat transfer of nanofluid utilizing Buongiorno's model in a wavy channel were analyzed and the simultaneous effects of Brownian motion and thermophoresis were discussed.
179 citations
Cites background from "Investigation on Convective Heat Tr..."
...Xuan and Li [23,24] have examined experimentally thermal conductivity and conductivity heat transfer feature and flow performance of copper-water nanofluid....
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TL;DR: In this article, the nanofluid was used as a working medium for a 1-mm wick-thickness sintered circular heat pipe and the experiment was performed to measure the temperature distribution and compare the heat pipe temperature difference using nanoffluid and DI-water.
178 citations
TL;DR: The maximum thermal conductivity enhancement and minimum viscosity increase are obtained using a lengthy sonication, which may have implications on application.
Abstract: The preparation of nanofluids is very important to their thermophysical properties. Nanofluids with the same nanoparticles and base fluids can behave differently due to different nanofluid preparation methods. The agglomerate sizes in nanofluids can significantly impact the thermal conductivity and viscosity of nanofluids and lead to a different heat transfer performance. Ultrasonication is a common way to break up agglomerates and promote dispersion of nanoparticles into base fluids. However, research reports of sonication effects on nanofluid properties are limited in the open literature. In this work, sonication effects on thermal conductivity and viscosity of carbon nanotubes (0.5 wt%) in an ethylene glycol-based nanofluid are investigated. The corresponding effects on the agglomerate sizes and the carbon nanotube lengths are observed. It is found that with an increased sonication time/energy, the thermal conductivity of the nanofluids increases nonlinearly, with the maximum enhancement of 23% at sonication time of 1,355 min. However, the viscosity of nanofluids increases to the maximum at sonication time of 40 min, then decreases, finally approaching the viscosity of the pure base fluid at a sonication time of 1,355 min. It is also observed that the sonication process not only reduces the agglomerate sizes but also decreases the length of carbon nanotubes. Over the current experimental range, the reduction in agglomerate size is more significant than the reduction of the carbon nanotube length. Hence, the maximum thermal conductivity enhancement and minimum viscosity increase are obtained using a lengthy sonication, which may have implications on application.
177 citations
Cites background from "Investigation on Convective Heat Tr..."
...For the viscosity of nanofluids, some researchers found no significant change compared to the base fluid [7]....
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TL;DR: In this paper, a review of different synthesis techniques and important physical properties (thermal conductivity and viscosity) that need to be considered very carefully during the preparation of TiO2 nanofluids for desired applications is presented.
Abstract: Titanium dioxide (TiO2) has been used extensively because of its unique thermal and electric properties. Different techniques have been used for the preparation of TiO2 nanofluids which include single-step and two-step methods. In the natural world, TiO2 exists in three different crystalline forms as anatase, brookite, and rutile. Nanoparticles are not used directly in many heat transfer applications, and this provides a major challenge to researchers to advance towards stable nanofluid preparation methods. The primary step involved in the preparation of nanofluid is the production of nano-sized solid particles by using a suitable technique, and then these particles are dispersed into base fluids like oil, water, paraffin oil or ethylene glycol. However, nanofluid can also be prepared directly by using a liquid chemical method or vapor deposition technique (VDT). Nanofluids are mostly used in heat transfer applications and the size and cost of the heat transfer device depend upon the working fluid properties, thus, in the past decade scientists have made great efforts to formulate stable and cost-effective nanofluids with enhanced thermophysical properties. This review focuses on the different synthesis techniques and important physical properties (thermal conductivity and viscosity) that need to be considered very carefully during the preparation of TiO2 nanofluids for desired applications.
177 citations
References
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Book•
01 Jan 1985
TL;DR: In this article, the physical concepts and methodologies of heat and mass transfer are explained for advanced undergraduate engineering majors, using a systematic method for problem solving and discusses the relationship of heat transfer to many important practical applications through examples and problems.
Abstract: This book, designed for advanced undergraduate engineering majors, explains the physical concepts and methodologies of heat and mass transfer. It uses a systematic method for problem solving and discusses the relationship of heat and mass transfer to many important practical applications through examples and problems. A and significant contribution is the extensive use of the First Law of thermodynamics.
4,113 citations
TL;DR: In this article, the authors used a Brookfield rotating viscometer to measure the viscosities of the dispersed fluids with γ-alumina (Al2O3) and titanium dioxide (TiO2) particles at a 10% volume concentration.
Abstract: Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...
3,730 citations
3,019 citations
"Investigation on Convective Heat Tr..." refers background in this paper
...Hamilton and Crasser (1962) have developed a more elaborate model for the effective thermal conductivity of twocomponent mixtures as a function of the conductivity of the pure materials, the composition of the mixture, and the shape of the dispersed particles....
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TL;DR: In this paper, a transient hot-wire method was used to measure the thermal conductivity of a small amount of nanoparticles and the experimental results showed that these nanoparticles have substantially higher thermal conductivities than the same liquids without nanoparticles.
Abstract: Oxide nanofluids were produced and their thermal conductivities were measured by a transient hot-wire method. The experimental results show that these nanofluids, containing a small amount of nanoparticles, have substantially higher thermal conductivities than the same liquids without nanoparticles. Comparisons between experiments and the Hamilton and Crosser model show that the model can predict the thermal conductivity of nanofluids containing large agglomerated Al{sub 2}O{sub 3} particles. However, the model appears to be inadequate for nanofluids containing CuO particles. This suggests that not only particle shape but size is considered to be dominant in enhancing the thermal conductivity of nanofluids.
2,811 citations
TL;DR: In this article, the authors proposed two different approaches for deriving heat transfer correlation of the nanofluid, and investigated the mechanism of heat transfer enhancement of the nano-fluid.
2,355 citations