• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.176-177
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• 2006

Two kinds of alumina nanofluids are prepared by dispersing $Al_2O_3$ nanoparticles m transformer oil. The thermal conductivity of the nanoparticle-oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The $Al_2O_3$ nanoparticles at a volume of 0.5% can increase the thermal conductivity of the transformer oil by 5.7%, and the overall heat transfer coefficient by 20%. From the natural convection test using a prototype transformer, the cooling effect of $Al_2O_3$-oil nanofluids on the heating element and oil itself is confirmed. However, excessive quantities of the surfactant have a harmful effect on viscosity, and thus it is strongly recommended to control the addition of the surfactant with great care.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.293-299
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• 2011

To study the flow characteristics of water-based $Al_2O_3$ nanofluids according to the shape of the nanoparticles, we measure the pressure drop in a fully developed laminar flow regime. Water-based $Al_2O_3$ nanofluids of 0.3 Vol.% with sphere-, rod-, platelet-, and brick-shaped nanoparticles are manufactured by the two-step method. Zeta potential is measured to examine the suspension and dispersion characteristics, and TEM image is considered to confirm the shape characteristics of the nanoparticles. The experimental results show that the pressure drop of $Al_2O_3$ nanofluids depends on the shape of the nanoparticles although the nanofluids has same volume fraction of nanoparticles. This is explained by the surface area per unit mass of the nanoparticles and the size of the nanoparticles suspended in the base fluids.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.170-177
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• 2012

To apply the nanofluids into the general vapor compression cycle, basically have to know the thermal properties including thermal conductivity and dynamic viscosity. And needs to show the dispersion characteristics for various nanofluids and concentrations. So, firstly this study showed experimentally the thermal properties for various concentration (0.1%~0.7%, as mass balance) and temperature($20^{\circ}C{\sim}40^{\circ}C$) on $Al_2O_3$, $TiO_2$, and CuO nanofluids using base fluid as POE oil that has used in the scroll compressor for various refrigeration system. From the results, the dynamic viscosity of nanofluids was considerably changed from the base POE oil. And, the dispersion characteristics of various nanofluids using the simple methods like as analyzing the RGB value or measuring the sinking height of nanofluids were showed experimentally. Through the results, the dispersion characteristics of $Al_2O_3$ nanofluid was better than those of $TiO_2$, and CuO nanofluids not considering the real refrigeration cycle rurming conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.16-20
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• 2007

In this paper, convective heat transfer and flow characteristics of $Al_2O_3$ nanoparticles suspended in water flowing through uniformly heated tubes are experimentally investigated under laminar flow regime. The heat transfer coefficient and the pressure drop of nanoparticles suspended in water are experimentally presented according to the pumping power. In addition, the heat transfer coefficient and the pressure drop of $Al_2O_3$ nanoparticles suspended in water are compared with those of pure water under the fixed pumping power. It is shown that the heat transfer coefficient of $Al_2O_3$ nanofluids with 0.1% volume fraction is enhanced by about 12% although the increment of the pressure drop of those is 4% compared with those of pure water.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.165-169
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• 2008

Binary nanofluids(Binary mixture + nanoparticles) have been extensively paid attention for application in absorption system as a new working fluid. Thermal property evaluation of the new refrigerants is inevitable to apply them for actual system. The objectives of this paper are to measure the thermal conductivity of the binary nanofluids by the transient hot-wire method, and to assess the application possibility of the binary nanofluids for absorption system. It was found that the thermal conductivity of the binary nanofluids ($H_2O/LiBrAl_2O_3$) increased with increasing the concentration of the nanoparticles ($Al_2O_3$) and enhanced up to 27% at 0.1 vol % of the nanoparticles.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.124-129
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• 2008

The objectives of this paper are to examine the effect of nano-particles on the pool type absorption heat transfer enhancement and to find the optimal conditions to design a highly effective compact absorber for $NH_3/H_2O$ absorption system. The effect of $Al_2O_3$ and CNT particles on the absorption performance is studied experimentally. The experimental ranges of the key parameters are 20% of $NH_3$ concentration, $0{\sim}0.08%$ (volume fraction) of CNT particles, and $0{\sim}0.06%$ (volume fraction) of $Al_2O_3$ nano-particles. For the $NH_3/H_2O$ nanofluids, the heat transfer rate and absorption rate with 0.02 vol% $Al_2O_3$ nano-particles were found to be 28.9% and 17.8% higher than those without nano-particles, respectively. It is recommended that the concentration of 0.02 vol% of $Al_2O_3$ nano-particles be the best candidate for $NH_3/H_2O$ absorption performance enhancement.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.546-551
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• 2005

In this paper we report fluid flow characteristics of $AL_2O_3$ nanoparicles suspended in water. Especially, the effects of volume fraction with the range of 0.01% to 0.3% and inner diameter of tubes on the pressure drop and the effective viscosity of $AL_2O_3$ nanoparicles suspended in water are experimentally investigated. Experimental results are compared with analytic solution which can be derived with Einstein model. We confirm whether Einstein model which have been used to determine the effective viscosity of nanofluids is valid or not.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.11
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• pp.949-956
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• 2007

Pool boiling critical heat flux (CHF) of nanofluids with oxide nanoparticles of $TiO_2$ or $Al_2O_3$ was experimentally investigated under atmospheric pressure. The results showed that a dispersion of oxide nanoparticles significantly enhances the CHF over that of pure water. Moreover it was found that nanoparticles were seriously deposited on the heater surface during pool boiling of nanofluids. CHF of pure water on a nanoparticle-deposited surface, which is produced during the boiling of nanofluids, was not less than that of nanofluids. The result reveals that the CHF enhancement of nanofluids is absolutely attributed to modification of the heater surface by the nanoparticle deposition. Then, the nanoparticle-deposited surface was characterized with parameters closely related to pool boiling CHF, such as surface roughness, contact angle, and capillary wicking. Finally, reason of the CHF enhancement of nanofluids is discussed based on the changes of the parameters.

• Advances in nano research
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• v.15 no.3
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• pp.191-201
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• 2023

In order to develop better method to enhance and control the flow and heat transfer inside the radiator of electronic device, the synergistic effect of MHD nanofluids and porous medium on the flow and heat transfer in rectangular opened channel is simulated using Lattice Boltzmann method. Three nanofluids of CuO-water, Al₂O₃-water and Fe₃O₄-water are studied to analyze the influence of the type of nanofluid on the synergistic effect. The simulation results show that the porous medium can increase the flow velocity in fluid zone adjacent to the porous medium and enhance the heat transfer on the surface of the channel. Under no magnetic field, when the porosity of porous medium is 0.8, the Nusselt number is 4.46% higher than when the porosity is 0.9. Al₂O₃-water has the best heat transfer effect among the three nanofluids. At Ф=0.06, Ha=100, θ=90°, ε=0.9, Nu of Al₂O₃-water is 6.51% larger than that of CuO-water and 5.05% larger than that of Fe₃O₄-water. Magnetic field enhances seepage in porous medium and inhibits heat transfer in the bottom wall. When Ha=30 and 60, the inhibiting effect is the most significant as the magnetic field angle is 90°. And when Ha=100, the inhibiting effect is the most significant as the magnetic field angle is 120°.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.341-348
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• 2007

One of the controversial research issues on nanofluids is the temperature dependence of the thermal conductivity of nanofluids, that is, whether it will increase or decrease according to the temperature rise. To evaluate precisely the thermal conductivity behavior of nanofluids, a systematic way of validation experiments for the measuring instrument has been highly recommended. In this paper, procedure of the validation test for transient hot-wire method using the temperature dependence of the base fluids was explained comprehensively and the comparison of the temperature dependence of water-$Al_2O_3$ nanofluids is made between the present work and that of Das et al.