Showing papers on "Nanofluid published in 2009"
TL;DR: In this paper, the authors summarized the important published articles on the enhancement of the forced convection heat transfer with nanofluids, including simulations, simulations, and experimental results.
1,738 citations
Massachusetts Institute of Technology1, Illinois Institute of Technology2, Franklin W. Olin College of Engineering3, Kent State University4, Rensselaer Polytechnic Institute5, Texas A&M University6, Ulsan National Institute of Science and Technology7, Tokyo Institute of Technology8, University of Naples Federico II9, Sasol10, University of Leeds11, University of Pittsburgh12, Indian Institute of Technology Madras13, Université libre de Bruxelles14, Silesian University of Technology15, North Carolina State University16, IBM17, ETH Zurich18, The Chinese University of Hong Kong19, Stanford University20, University of Puerto Rico at Mayagüez21, South Dakota School of Mines and Technology22, Korea Aerospace University23, Nanyang Technological University24, Helmut Schmidt University25, National Institute of Standards and Technology26, Korea University27, Indian Institute of Technology Kharagpur28, Indira Gandhi Centre for Atomic Research29, Queen Mary University of London30, Argonne National Laboratory31
TL;DR: The International Nanofluid Property Benchmark Exercise (INPBE) as mentioned in this paper was held in 1998, where the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or "nanofluids" was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady state methods, and optical methods.
Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.
942 citations
TL;DR: In this article, the effects of particle volume fraction, temperature and particle size on thermal conductivity of alumina/water and copper oxide/water nanofluids were investigated.
886 citations
Journal Article•
TL;DR: The International Nanofluid Property Benchmark Exercise (INPBE) as discussed by the authors was held in 1998, where the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or "nanofluids" was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady state methods, and optical methods.
Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.
881 citations
TL;DR: In this article, the Cheng-Minkowycz problem of natural convection past a vertical plate, in a porous medium saturated by a nanofluid, is studied analytically.
760 citations
TL;DR: In this paper, a model was developed to account for the thermal conductivity of nanofluids as a function of temperature, particle volumetric concentration, the properties of nanoparticles, and the base fluid, which agrees well with the experimental data.
750 citations
TL;DR: In this paper, the thermal conductivity and viscosity of various shapes of alumina nanoparticles in a fluid consisting of equal volumes of ethylene glycol and water were investigated and accompanied by theoretical modeling.
Abstract: The thermal conductivity and viscosity of various shapes of alumina nanoparticles in a fluid consisting of equal volumes of ethylene glycol and water were investigated. Experimental data were analyzed and accompanied by theoretical modeling. Enhancements in the effective thermal conductivities due to particle shape effects expected from Hamilton–Crosser equation are strongly diminished by interfacial effects proportional to the total surface area of nanoparticles. On the other hand, the presence of nanoparticles and small volume fractions of agglomerates with high aspect ratios strongly increases viscosity of suspensions due to structural constrains. Nanoparticle surface charge also plays an important role in viscosity. It is demonstrated that by adjusting pH of nanofluid, it is possible to reduce viscosity of alumina nanofluid without significantly affecting thermal conductivity. Efficiency of nanofluids (ratio of thermal conductivity and viscosity increase) for real-life cooling applications is evaluate...
735 citations
TL;DR: In this article, a transient hot-wire apparatus is used for measuring the thermal conductivity of nanofluids whereas the Bohlin rotational rheometer (Malvern Instrument) is used to measure the viscosity of nanometres.
733 citations
TL;DR: In this paper, the authors summarize recent development in research on synthesis and characterization of stationary nanofluids and try to find some challenging issues that need to be solved for future research.
732 citations
TL;DR: In this article, a critical review of research on heat transfer applications of nanofluids with the aim of identifying the limiting factors so as to push forward their further development is presented.
697 citations
TL;DR: In this article, the authors investigated the feasibility of using a nonconcentrating direct absorption solar collector (DAC) and compared its performance with that of a typical flat-plate collector.
Abstract: Due to its renewable and nonpolluting nature, solar energy is often used in applications such as electricity generation, thermal heating, and chemical processing. The most cost-effective solar heaters are of the "flat-plate" type, but these suffer from relatively low efficiency and outlet temperatures. The present study theoretically investigates the feasibility of using a nonconcentrating direct absorption solar collector (DAC) and compares its performance with that of a typical flat-plate collector. Here a nanofluid-a mixture of water and aluminum nanoparticles—is used as the absorbing medium. A two-dimensional heat transfer analysis was developed in which direct sunlight was incident on a thin flowing film of nanofluid. The effects of absorption and scattering within the nanofluid were accounted for. In order to evaluate the temperature profile and intensity distribution within the nanofluid, the energy balance equation and heat transport equation were solved numerically. It was observed that the presence of nanoparticles increases the absorption of incident radiation by more than nine times over that of pure water. According to the results obtained from this study, under similar operating conditions, the efficiency of a DA C using nanofluid as the working fluid is found to be up to 10% higher (on an absolute basis) than that of a flat-plate collector. Generally a DAC using nanofluids as the working fluid performs better than a flat-plate collector, however, much better designed flat-plate collectors might be able to match or outperform a nanofluids based DAC under certain conditions.
TL;DR: In this article, an improved functionality of phase change materials (PCM) through dispersion of nanoparticles is described, which exhibit enhanced thermal conductivity in comparison to the base material.
TL;DR: In this article, the authors measured the pressure drop and convective heat transfer coefficient of water-based Al2O3 nanofluids flowing through a uniformly heated circular tube in the fully developed laminar flow regime.
TL;DR: Nanofluids are a new class of nanotechnology-based heat transfer fluids engineered by dispersing and stably suspending nanoparticles with typical length on the order of 1-50 nm in traditional heat transfer fluid.
Abstract: Nanofluids are a new class of nanotechnology-based heat transfer fluids engineered by dispersing and stably suspending nanoparticles with typical length on the order of 1-50 nm in traditional heat transfer fluids. For the past decade, pioneering scientists and engineers have made phenomenal discoveries that a very small amount (<1 vol %) of guest nanoparticles can provide dramatic improvements in the thermal properties of the host fluids. For example, some nanofluids exhibit superior thermal properties such as anomalously high thermal conductivity at low nanoparticle concentrations, strong temperature- and size-dependent thermal conductivity, a nonlinear relationship between thermal conductivity and concentration, and a threefold increase in the critical heat flux at a small particle concentration of the order of 10 ppm. Nanofluids are of great scientific interest because these unprecedented thermal transport phenomena surpass the fundamental limits of conventional macroscopic theories of suspensions. Therefore, numerous mechanisms and models have been proposed to account for these unexpected, intriguing thermal properties of nanofluids. These discoveries also show that nanofluids technology can provide exciting new opportunities to develop nanotechnology-based coolants for a variety of innovative engineering and medical applications. As a result, the study of nanofluids has emerged as a new field of scientific research and innovative applications. Hence, the subject of nanofluids is of great interest worldwide for basic and applied research. This paper highlights recent advances in this new field of research and shows future directions in nanofluids research through which the vision of nanofluids can be turned into reality.
TL;DR: In this paper, the effect of particle size on convective heat transfer in laminar developing region was evaluated with alumina-water nanofluids in tube flow with constant heat flux.
TL;DR: In this article, the effect of nanofluids on convective heat transfer was investigated through a circular straight tube with a constant heat flux condition in the laminar and turbulent flow regime.
TL;DR: In this paper, heat transfer and viscous pressure loss were investigated for alumina-water and zirconia-water nanofluids in a flow loop with a vertical heated tube.
TL;DR: In this article, the effect of dispersing energy (ultrasonication) on viscosity, thermal conductivity, and the laminar convective heat transfer was studied.
TL;DR: In this article, a new equation for calculating the nanofluid viscosity by considering the Brownian motion of nanoparticles is introduced, where the relative velocity between the base fluid and nanoparticles has been taken into account.
Abstract: In this paper a new equation for calculating the nanofluid viscosity by considering the Brownian motion of nanoparticles is introduced. The relative velocity between the base fluid and nanoparticles has been taken into account. This equation presents the nanofluid viscosity as a function of the temperature, the mean nanoparticle diameter, the nanoparticle volume fraction, the nanoparticle density and the base fluid physical properties. In developing the model a correction factor is introduced to take into account the simplification that was applied on the boundary condition. It is calculated by using very limited experimental data for nanofluids consisting of 13 nm Al2O3 nanoparticles and water and 28 nm Al2O3 nanoparticles and water. The predicted results are then compared with many other published experimental results for different nanofluids and very good concordance between these results is observed. Compared with the other theoretical models that are available in the literature, the presented model, in general, has a higher accuracy and precision.
TL;DR: In this paper, thermal transport properties including thermal conductivity and viscosity of ZnO-EG-based nanofluids were measured, and the results showed that the thermal conductivities of these nanoflugs are independent of setting time from 20 to 360 min.
TL;DR: In this article, the effect of inclination angle on convection heat transfer and fluid flow in a two-dimensional enclosure filled with Cu-nanofluid has been analyzed numerically.
TL;DR: In this paper, an experimental study on the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 0.2 vol.% TiO2 nanoparticles was performed.
TL;DR: In this paper, Al2O3-H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration.
TL;DR: In this paper, the authors present a numerical study of the cooling performance of a heat source embedded on the bottom wall of an enclosure filled with nanofluids, where the top and vertical walls of the enclosure are maintained at a relatively low temperature.
Abstract: This article presents a numerical study of natural convection cooling of a heat source embedded on the bottom wall of an enclosure filled with nanofluids. The top and vertical walls of the enclosure are maintained at a relatively low temperature. The transport equations for a Newtonian fluid are solved numerically with a finite volume approach using the SIMPLE algorithm. The influence of pertinent parameters such as Rayleigh number, location and geometry of the heat source, the type of nanofluid and solid volume fraction of nanoparticles on the cooling performance is studied. The results indicate that adding nanoparticles into pure water improves its cooling performance especially at low Rayleigh numbers. The type of nanoparticles and the length and location of the heat source proved to significantly affect the heat source maximum temperature.
TL;DR: In this article, the onset of convection in a horizontal layer of a porous medium saturated by a nanofluid is studied analytically, and it is found that the critical thermal Rayleigh number can be reduced or increased by a substantial amount depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy, by the presence of the nanoparticles.
TL;DR: In this paper, the authors present new data for the thermal conductivity enhancement in seven nanofluids containing 8-282-nm diameter alumina nanoparticles in water or ethylene glycol.
Abstract: We present new data for the thermal conductivity enhancement in seven nanofluids containing 8–282 nm diameter alumina nanoparticles in water or ethylene glycol. Our results show that the thermal conductivity enhancement in these nanofluids decreases as the particle size decreases below about 50 nm. This finding is consistent with a decrease in the thermal conductivity of alumina nanoparticles with decreasing particle size, which can be attributed to phonon scattering at the solid–liquid interface. The limiting value of the enhancement for nanofluids containing large particles is greater than that predicted by the Maxwell equation, but is predicted well by the volume fraction weighted geometric mean of the bulk thermal conductivities of the solid and liquid. This observation was used to develop a simple relationship for the thermal conductivity of alumina nanofluids in both water and ethylene glycol.
TL;DR: In this article, the Nusselt number prediction for nanofluids has been validated with existing well established correlations, and it is found that smaller diameter nanoparticles have higher viscosity.
TL;DR: In this paper, different viscosity and thermal conductivity models are used to evaluate heat transfer enhancement in horizontal annuli using variable properties of Al2O3-water nanofluid.
TL;DR: In this article, an integrated microsystem consisting of a single microchannel on one side, and two localized heaters and five polysilicon temperature sensors along the channel on the other side were fabricated.