• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.85-91
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• 2011

Computational results with pseudoplastic fluid flows for fully developed non-Newtonian laminar flows have been obtained. Those consist of the product of friction factor and Modified Reynolds number and Nusselt numbers with respect to the shear rate parameter in an annular pipe. The numerical results of the product of friction factor and Reynolds numbers and the Nusselt numbers for both Newtonian region and the power law region were compared with previously published asymptotic results, respectively. In the present calculations, the product of friction factor and Newtonian Reynolds numbers for pseudoplastic fluid at power law region in annular pipe is 180% less than that for Newtonian fluid. For power law fluids with different power law flow indices, the difference of the product of friction factor and power law Reynolds number between previous and the present results at the power law region is within 0.20%. The solutions also show the effect of the shear rate parameter on the Nusselt number and about 11% increase of Nusselt number at the power region.

• Clean Technology
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• v.13 no.2
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• pp.151-158
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• 2007

An experimental study to investigate the condensing heat transfer characteristics of small diameter horizontal double pipe heat exchangers with R-22 and R-410A was performed. Experimental facility was constructed to calculate and observe HTC(heat transfer coefficients), flow patterns and pressure drop. The main components include a liquid pump, an evaporator, a condenser(test section), a sight-glass, pressure taps and measurement apparatus. Two pipes of different diameters are tested; One 5.35 mm ID 0.5 mm thick, the other 3.36 mm ID 0.7 mm thick. The mass flow rate ranged from 200 to $500\;ks/m^2{\cdot}s$ and heating capacity were form 1.0 to 2.4 kW. The flow patterns of R-22 and R-410A were observed with a high speed camera through the sight-glass. The tests revealed that HTC of R-410A was higher than that of R-22 by maximum 5%. Annular pattern was observed for the most cases but stratified flow was also detected when x<0.2. The pressure drop in 3.36 mm ID pipe was higher than that of 5.35 mm by $30{\sim}50%$. Comparing with previous correlations such as Shah, Fujii and Soliman's, Fujii' showed the best good agreement with my data with a maximum deviation of 40%.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.629-638
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• 2014

Objective of this study is to be utilized as foundational data of expression methods and to increase children's dream and imagination by researching and analyzing differences of imaginative reaction from patterns of imaginative activities and verbal response for the expressive methods of illustrations. Study subjects are 253 children aged from six to seven years old, and four different types of research tool of which are screens with simple pattern, realistic pattern, omitted pattern and indirect pattern has been used in the empirical survey conducted over two times. Result from provided research tools has shown that difference of diversity can be observed from patterns of imaginative activities and verbal reaction patterns. Especially, in terms of imaginative activities, structural and creative imagination responses can be observed from screens with simple, omitted patterns and indirect and metaphorical patterns compares to screens with simple patterns and direct, realistic patterns, and positive affection to children's dream and creativity and imagination can be found from the result of high imaginative response observed from patterns of verbal reaction.

• Solar Energy
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• v.12 no.3
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• pp.47-59
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• 1992

In the concentric tube type recuperator, which is the most typical type of radiation recuperator, installed on the exhaust-secion of industrial furnace, air flows between the adiabatic outer tube and the inner tube in which exhausted gas flows with high temperature. The waste heat of the exhausted gas is transferred to the inner tube, and transferred from the inner tube to the flowing air. The heat transfer by radiation In the concentric tube type recuperator is modeled using spherical harmonics approximation, namely, P-N method and numerically analyzed considering the effect of dynamic flow field. The results are compared with the existing empirical data. In addition, a theoretical method is presented for the analysis of the heat transfer characteristics of a recuperator with a reradiator installed in the inner tube, which causes re-radiant in the inner tube, and the characteristics of the recuperator is analyszed and defined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1111-1119
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• 2010

In this study, condensation heat transfer coefficients of R-410A were obtained in flattened tubes made from round tubes with an inner diameter of 5.0 mm. The saturation temperature was $45^{\circ}C$; the heat flux, 10 kW/$m^2K$; the mass flux, 100-400 kg/$m^2s$; and the quality, 0.2-0.8. The results showed that the effect of the aspect ratio on the condensation heat transfer coefficient depended on the flow pattern. For annular flow, the heat transfer coefficient increased as the aspect ratio increased. For stratified flow, however, the reverse was true: the pressure drop increased as the aspect ratio increased. Existing correlations adequately predicted the heat transfer coefficients and pressure drops of the flattened tubes.

• Journal of the Korean Institute of Gas
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• v.6 no.1 s.17
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• pp.38-45
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• 2002

Hydrates are solid cryctallines resembling ice in appearance, which are consist of a gas molecule surrounded by a cage of water molecules. Because of containning a large amount of methane, hydrates have been considered as a future energy resource. However, the formation of hydrates in the oil and gas industries has been known as a serious problem for a long time. The formation of hydrate in pipeline is common in seasonally cold or sub-sea environments with low temperatures and high pressures. Especially, hydrate plug formation becomes a real menace to flow assurance in inadequately protected transmission lines. This study was carried out for the purpose of understanding mechanism of hydrate plugging and examining formation conditions of hydrate in high pressure gas pipeline. In this study, we measured hydrate equilibrium conditions under the various flowing conditions with the methane. The results were presented both the plugging tendency and the effect of flowing velocity.

• (The)Study of the Eastern Classic
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• no.34
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• pp.339-362
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• 2009

If we try to define the concept of beauty in the large sense, as Kant and Chaung-tzu all agree, It can not be fixed in the one sense, but whose connotation and denotation should be extended infinitely. In this sense, I would like to say that the beauty is liberty. Aesthetics of Kant is oriented toward subjective and reflexive dimension, while that of Chuang-tzu is oriented toward natural and practical one. The difference between aesthetics of the two philosophers begins from their philosophical methodology. If the transcendental methode which is proper to Kant's philosophy prefers to discriminate and devide everything especially from dichotomic viewpoint by langage. But Chuang-tzu' methode called Za-Mang criticizes such a dichotomic division and langage itself. Even so, the two in the long run agree as to the foundation of beauty. But Kant's liberty is one of will or transcendental, meanwhile that of Chuang-tzu is based on recognize the fact that we are all production of nature. according to Chuang-tzu, in the great beginning, there was non-being. It had neither being nor name. The One originates from it. When things obtain it and come into existence. As the One, Tao is in the excrement and urine. Everything is under the constant flux. All species have originative or moving power. Although the universe is vast, its transformation is uniform. Because all things are one. Vacuity, tranquillity, mellowness, quietness, and taking no action characterize the things of universe at peace and represent the ultimate of Tao and virtue. The material was transformed to be form, form was transformed to become life, and now life has transformed to become death. A basic principle of Chuang-tzu's art is expressed in the phrase "taking off clothes and squatting down bare-backed". The key of Chuang-tzu's aesthetics is to dedicate to the expression of inner spirit instead of physical verisimilitude, and painting should be a spontaneous and instantaneous flow of the brush. Kant's concepts such as "disinterested" and "purposiveness of nature" seem to imply in the long run the unification of nature and human being which is fundament to Chuang-tzu's aesthetics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.761-772
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• 2015

Microfin tubes having an outside diameter (O.D.) of 7.0 mm are widely used in residential air conditioning systems and heat pumps. It is known that the mass fluxes for air conditioners and heat pumps under partial load conditions are several tens of $kg/m^2s$. However, literature surveys reveal that previous investigations were limited to mass flux over $100kg/m^2s$. In this study, we conduct R-410A evaporation heat-transfer tests at low mass fluxes ($50-250kg/m^2s$) using a 7.0 mm O.D. microfin tube. During the test, the saturation temperature was maintained at $8^{\circ}C$, and the heat flux was maintained at $4.0kW/m^2$. For comparison purposes, we also test a smooth tube with a 7.0 mm O.D. The results showed that the heat-transfer enhancement factor of the microfin tube increased as the mass flux decreased up to $150kg/m^2s$, which decreased as the mass flux further decreased. The reason for this was attributed to the change of the flow pattern from an annular flow to a stratified flow. Within the test range, the frictional pressure drops of the microfin tube were approximately the same as those of the smooth tube. We then compare experimental data obtained with the predictions obtained for the existing correlations.