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.
Citations
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TL;DR: In this paper, a new approach of enhanced artificial neural network (EANN) is developed based on the new generated hybrid nanocomposite of F-MWCNTs and Fe3O4/EG which represents the Functionalized Multi Walled Carbon Nano Tubes together with Fe 3O4 nanoparticles, dispersed in ethylene glycol as the base fluid.
Abstract: The new approach of “enhanced artificial neural network” (EANN) is developed based on the new generated hybrid nanocomposite of F-MWCNTs–Fe3O4/EG which represents the Functionalized Multi Walled Carbon Nano Tubes together with Fe3O4 nanoparticles, dispersed in ethylene glycol (EG) as the base fluid. Moreover, a new suitable sensitivity analysis is presented which involves a novel proposed method for the sensitivity analysis via ANNs. In this method, the sensitivity of the outputs predicted by means of an ANN to the inputs is calculated analytically rather than numerically. The proposed method not only provides more perceptive, precise and accurate results, but also requires less computational time and cost. The proposed method can be used for all ANNs having various architectures, training algorithms and input–output data sets.
129 citations
TL;DR: In this paper, the authors reported measurements of the effective thermal conductivity of dispersions of single-walled carbon nanotube (SWNT) suspensions in ethylene glycol.
128 citations
TL;DR: In this article, the entropy generation in natural convection of nanofluid in a wavy cavity using a single-phase model was analyzed using the finite difference method of the second-order accuracy.
Abstract: Purpose
The main purpose of this numerical study is to study on entropy generation in natural convection of nanofluid in a wavy cavity using a single-phase nanofluid model.
Design/methodology/approach
The cavity is heated non-uniformly from the wavy wall and cooled from the right side while it is insulated from the horizontal walls. The physical domain of the problem is transformed into a rectangular geometry in the computational domain using an algebraic coordinate transformation by introducing new independent variables ξ and η. The governing dimensionless partial differential equations with corresponding initially and boundary conditions were numerically solved by the finite difference method of the second-order accuracy. The governing parameters are Rayleigh number (Ra = 1000-100000), Prandtl number (Pr = 6.82), solid volume fraction parameter of nanoparticles (φ = 0.0-0.05), aspect ratio parameter (A = 1), undulation number (κ = 1-3), wavy contraction ratio (b = 0.1-0.3) and dimensionless time (τ = 0-0.27).
Findings
It is found that the average Bejan number is an increasing function of nanoparticle volume fraction and a decreasing function of the Rayleigh number, undulation number and wavy contraction ratio. Also, an insertion of nanoparticles leads to an attenuation of convective flow and enhancement of heat transfer.
Originality
The originality of this work is to analyze the entropy generation in natural convection within a wavy nanofluid cavity using single-phase nanofluid model. The results would benefit scientists and engineers to become familiar with the flow behaviour of such nanofluids, and will be a way to predict the properties of this flow for the possibility of using nanofluids in advanced nuclear systems, in industrial sectors including transportation, power generation, chemical sectors, ventilation, air-conditioning, etc.
128 citations
TL;DR: In this article, the steady stagnation point flow of a Casson nano fluid in the presence of convective boundary conditions is investigated. And the resulting ordinary differential equations are successfully solved analytically using Optimal Homotopy analysis method (OHAM) via BVPh2.0.
127 citations
TL;DR: In this article, the authors investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al 2O3+Ag) nanofluids in a wide rectangular micro-channel.
Abstract: Laminar forced convection flow of nanofluids in a wide rectangular micro-channel has been numerically studied. The present study investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al2O3+Ag) nanofluids in a micro-channel. The conduction phenomena of the solid region show a significant effect on the heat transfer characteristics of nanofluid. Hence, the channel is considered with finite thickness on its bottom to accommodate heat source or electronic component and a uniform heat flux is applied to the three sides of the solid region. A two-dimensional conjugate heat transfer homogeneous phase model has been developed and results are reported for different Reynolds numbers. The governing equations are solved by Simplified Marker and Cell (SMAC) algorithm on non-staggered grid using finite volume method. The effects of Reynolds number, pure nanoparticles volume concentration, hybrid nanoparticles mixture volume concentrations and nanoparticles size on the flow and heat transfer characteristics are reported. The results show that the average convective heat transfer coefficient increases with increase in nanoparticles volume concentration and Reynolds number. The nanofluids obtained by dispersing nanoparticles such as Al2O3, Ag and hybrid (Al2O3+Ag) in the base fluid shows a significant enhancement of average convective heat transfer coefficient in comparison with pure water. It is also observed that 3 vol.% hybrid nanofluid (0.6 vol.% Al2O3+2.4 vol.% Ag) shows higher average convective heat transfer coefficient than that of pure water, pure oxide (Al2O3) and pure metallic (Ag) nanofluids. The study presents that hybrid nanofluids are the new class of working fluids with less volume concentration of metallic (Ag) nanoparticles. Moreover, use of hybrid nanofluids at high volume concentration reduces the cost of the working fluid and enhances the heat transfer characteristics in comparison with that of metallic nanofluids. The interface temperature between solid and fluid regions are reported for different nanofluids. The size of the nanoparticle shows significant effect on heat transfer characteristics. The present results are matching with the numerical and experimental results available in the literature.
127 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