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Seokwon Kim

Bio: Seokwon Kim is an academic researcher from Korea University. The author has contributed to research in topics: Nanofluid & Thermal conductivity. The author has an hindex of 7, co-authored 9 publications receiving 1924 citations.

Papers
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Journal ArticleDOI
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

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

Journal ArticleDOI
TL;DR: In this article, an EG-based ZnO nanofluid with a high-resolution transmission electron microscopy (TEM) was used to study the structural properties of the ZnOs.

91 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the spray and atomization behavior of 0.35% C934 Carbopol gels with or without 15 wt. SUS304 nanoparticles of 100 nm using a doublet like-on-like impinging jet system.
Abstract: We have investigated the spray and atomization behavior of 0.35% C934 Carbopol gels with or without 15 wt.% SUS304 nanoparticles of 100 nm using a doublet like-on-like impinging jet system (orifice diameter of 0.7 mm, impingement angle 2h of 90) and compared with the spray behavior of water. The spray patterns of gel materials were qualitatively different from those of water and could be divided into four types: open rim and no shedding drop; rimless sheet with ray shaped shedding; sheet with ligament separation; fully developed. The sheet sizes of water and the pure Carbopol gel increased with the increase in jet velocity, but the sheet size of the Carbopol gel containing SUS particles did not change with the increase in velocity. The aspect ratio (Lmax/Wmax) of the sheet was constant at 2.1 for water and 1.7 for two gel materials. Due to the high viscosity of gel materials, the amplification of sinusoidal waves was mitigated and the spreading angle was smaller when compared with water. The breakup length of the pure Carbopol gel was longer than that of water. However the breakup length of the Carbopol gel containing SUS particles was remarkably shorter than that of the pure Carbopol gel due to the increase in impact energy by the heavy particles as well as the decrease in gel strength by the addition of nanoparticles. The drop Sauter mean diameter (SMD) decreased with the increase in jet velocity, and it converged to an asymptotic value. The asymptotically convergent drop SMD of water was about 100 lm while that of Carbopol gels was 75–77 lm. The elasticity of gels appears to reduce the asymptotic drop size.

56 citations

Journal ArticleDOI
TL;DR: In this paper, the thermal conductivity of nanofluids with the characterized dispersion status was investigated and it was concluded that the Brownian motion plays a key role in enhancing thermal conductivities.
Abstract: Nanofluid is a novel heat transfer fluid prepared by dispersing nanometer-sized solid particles in a traditional heat transfer fluid for heat transfer enhancement. The microstructure investigation of nanofluids by rheological techniques shows that the particles do not exist as individual particles and nanofluids of rodlike alumina nanoparticles have a sol- or weakly flocculated gel-structure depending on particle concentration. The rate of thermal conductivity increase with concentration is faster in the sol state than in the weakly flocculated gel state. When the nanofluid becomes a strongly flocculated gel thermal conductivity remains almost the same as the pure liquid value. It is concluded that the Brownian motion plays a key role in enhancing thermal conductivity. The present study is the first report on the thermal conductivity of nanofluids with the characterized dispersion status.

35 citations


Cited by
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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

Journal ArticleDOI
TL;DR: Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995 as mentioned in this paper, and there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10).
Abstract: Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.

679 citations

Journal ArticleDOI
TL;DR: In this article, the effect of nanoparticle volume fraction on thermal conductivity and dynamic viscosity of Ag-MgO/water hybrid nanofluid with the particle diameter of 40(mgO) and 25(Ag) nm was investigated.

461 citations

Journal ArticleDOI
TL;DR: Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed.
Abstract: Nanofluids, i.e., well-dispersed (metallic) nanoparticles at low- volume fractions in liquids, may enhance the mixture’s thermal conductivity, knf, over the base-fluid values. Thus, they are potentially useful for advanced cooling of micro-systems. Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed. It is evident that key questions still linger concerning the best nanoparticle-and-liquid pairing and conditioning, reliable measurements of achievable knf values, and easy-to-use, physically sound computer models which fully describe the particle dynamics and heat transfer of nanofluids. At present, experimental data and measurement methods are lacking consistency. In fact, debates on whether the anomalous enhancement is real or not endure, as well as discussions on what are repeatable correlations between knf and temperature, nanoparticle size/shape, and aggregation state. Clearly, benchmark experiments are needed, using the same nanofluids subject to different measurement methods. Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results. Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight. Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

434 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarized the important results regarding the improvement in the thermophysical properties of nanofluids and identified the opportunities for future research in the field of nanophotonics.
Abstract: This paper summarizes the important results regarding the improvement in the thermophysical properties of nanofluids. The influence of important parameters like particle's (loading, material, size, and shape), base fluid type, temperature, additives and pH value has been considered. There are many conflicting reports on the influence of parameters on thermophysical properties and the literature in this field is widespread, so this article would be beneficial for investigators to have a precise screening of a broad range of studies in this field. Further literature review of the applications of nanofluids with a particular focus on the advantages of using nanofluids in solar collectors and as coolants in automotive heat exchangers. The authors hope that this review can help in the translation of nanofluid technology from the lab scale research to industrial applications in solar collectors and automotive sector. At last, the paper identifies the opportunities for future research.

408 citations