• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.97-103
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• 2005

In this paper, effects on the heat transport limitation of heat pipe by the wick structural factors were theoretically analyzed for the sintered-copper wick heat pipe. Uniformity of particle size and sintering process were acted as dominant factors on the pore distribution and wick porosity, and small deviations of the wick thickness and the pore size greatly affected the heat transport limitations of the heat pipe. Especially, slight variations of the wick thickness, mean particle radius and capillary radius along the vapor temperatures and inclination angles remarkably changed the capillary limitation of the heat pipe.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.16-25
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• 2004

Theoretical analysis for predicting the heat transport limitation of a copper powder sintered wick heat pipe was performed. The heat pipe diameter was 8mm and water was used for working fluid. The particle diameter was classified by 5 different meshes, and each capillary pressures and heat transport limitations. thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius($r_c$), porosity($\varepsilon$), Permeability (K). The wick capillary limitation was increased according as the particle diameter and the wick thickness and the operating temperature were increased. As the porosity and the capillary radius were larger. then the heat transport limitation was higher. The thermal resistance was greatly increased according as the wick thickness was increased.

• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.17-25
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• 1996

Usual experimental adsorption isotherms as a function of relative humidity were constructed from adsorbed water contents in soils, which were kept more than 2 days in vacuum desiccators with constant humidities controlled by sulfuric acids of various concentrations. From the experimental data, the adsorption surface areas were calculated on the basis of the existing adsorption theory, such as Langmuir, BET, and Aranovich. Based on the Gibbs function describing chemical potential of perfect gas, the relative humidities in the desiccators were transformed into their chemical potentials, which were assumed to be the same as the potentials of equilibratedly adsorbed water in soils. Moreover, the water potentials were again transformed into the equivalent capillary pressures, heads of capillary rise, and equivalent radius of capillary pores, on the basis of Laplace equation for surface tension pressure of spherical bubbles in water. Adsorption quantity distributions were calculated on the profile of chemical potentials of the adsorbed water, equivalent adsorption and/or capillary pressures, and equivalent capillary radius. The suggested theories were proved through its application for the prediction of temperature rise of sulfuric acid due to hydration heat. Adsorption heat calculated on the basis of the potential difference was dependant on various factors, such as surface area, equilibrium constants in Langumuir, BET, etc.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.27-34
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• 2006

Although the importance of size-resolved raindrops study has been known, it has not been popularized up to the present. In the present study, an attempt was made to generalize the size-resolved raindrops study by a combination of the frozen raindrop collection method and a commercially available high-performance capillary electrophoresis (HPCE). Samplings were carried out at Kyoto, Japan in October 2002. The inorganic ions (chloride, nitrate, sulphate, calcium, ammonium, sodium, magnesium, potassium) in size classified raindrop samples were successfully analyzed by HPCE with good repeatability. To assure the accuracy and precision of HPCE data, t-test was conducted with paired analytical data, which were experimentally constructed by analyzing standard solutions with HPCE and IC, respectively. T-test showed that there is no notable difference between the concentrations determined by the two analytical methods. Every ionic concentration in both cation and anion was found to be strong raindrop size dependence. Though there was slight increase of sodium and sulphate concentrations between 0.85 mm and 1.15 mm raindrop radius, it showed a strong decrease for every ionic component with increasing droplet radius. The combination of the frozen raindrop collection method and a commercially available HPCE can meet the need of size-resolved raindrops study.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.23-28
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• 1985

A model for degradation of $eta$-$Al_2O_3$ is derived from sress generated by Poiseuille pressure capillary effect and effulent flux in charging process of Na-S Battery. Critical current density for degradation increase with increasing the crack length and crack tip radius. radius 10-7cm and crack length 10-5cm Dependence of crack growth velocity on crack lengh is seperated two regions that is for a large crack length it is predominated by Poiseuille pressure and effulent fluex but in the case of small crack length it is controlled by capillary effect.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.176-184
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• 1999

Numerical and experimental studies were performed to examine the characteristics of heat and mass transfer processes for a Micro Heat Pipe(MHP) with a triangular cross-section. Solutions on mass flow rate, pressure variation, and radius of meniscus were obtained using the mathematical model developed by Faghri and Khrustalev. To obtain an increase in capillary limitation, a triangular tube with curved walls was designed and fabricated. The measurement by microscope showed that the radius at corners of the tube was ranging between 0.03-0.05mm. Performance test for MHPs using the triangular tube with curved walls proved a substantial increasement in heat transport limitation, with 4.5W and 2.0W in case of using water and ethanol as a working fluid, respectively. In the previous study by Faghri a limitation of 0.5W was reported for a water MHP with a regular triangular tube.

• Computers and Concrete
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• v.4 no.2
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• pp.157-166
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• 2007

The paper considers a theoretical model to study sulfate ion diffusion in saturated porous media - cement based mineral composites, accounting for simultaneous effects, such as filling micro-capillaries (pores) with ions and chemical products and liquid push out of them. Pore volume change and its effect on the distribution of ion concentration within the specimen are investigated. Relations for the distribution of the capillary relative radius and volume within the composite under consideration are found. The numerical algorithm used is further completed to consider capillary size change and the effects accompanying sulfate ion diffusion. Ion distribution within the cross section and volume of specimens fabricated from mineral composites is numerically studied, accounting for the change of material capillary size and volume. Characteristic cases of 2D and 3D diffusion are analyzed. The results found can be used to both assess the sulfate corrosion in saturated systems and predict changes occurring in the pore structure of the composite as a result of sulfate ion diffusion.

• Tribology and Lubricants
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• v.17 no.3
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• pp.191-197
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• 2001

Nano adhesion and friction characteristics between SPM(scanning electron microscope) tips and flat plates of different materials were experimentally studied. Tests were performed to measure adhesion and friction in AFM(atomic force microscope) and LFM(lateral force microscope) modes in different conditions of relative humidity. Three different Si$_3$N$_4$ tips (rdaii : 15nm, 22nm and 50 nm) and three different flat plates of Si-wafer(100), W-DLC(tungsten-incorporated diamond-like carbon) and DLC were used. Results generally showed that adhesion and friction increased with the tip radius, and W-DLC and DLC surfaces were superior to Si-wafer. But the adhesion force of Si-wafer showed non linearity with the tip radius while W-DLC and DLC surfaces showed good correlation to the “JKR model”. It was found that high adhesion force between Si-wafer and a large radius of tip was caused by a capillary action due to the condensed water.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.127-135
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• 2006

Experimental studies of the cylindrical sintered-copper wick heat pipes were carried out to investigate the capillary heat transfer characteristics. Six models of the sintered-copper wick heat pipes were manufactured and tested to evaluate the heat transport limitations and the thermal characteristics. Also the performance of the heat pipes was analyzed theoretically and compared with the test results. The heat pipe models are divided into two sintered-wick groups and the nominal particle sizes are $180{\mu}m$(wick #1) and $200{\mu}m$(wick #2) respectively The experimental results showed that, the porosity of wick #1 was higher than that of wick #2, and also the wick #1 was generally superior than the wick #2 for the heat transport capability. The maximum heat transport rates were increased as the wick thicknesses and the vapor temperatures were increased.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.662-669
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• 2000

Based on the viscous flow characteristics of gas through capillary tube, a simple and low cost system was developed for controlling gas concentration for use in C.A experiments. The gas flow rate through capillary tube had a linear relationship with pressure, $(length)^{-1}$ and $(radius)^4$ of capillary tube, which agreed well with Hagen-Poiseuille's law. The developed system could control the gas concentration in storage chamber within ${\pm}0.3%$ deviation compared to the preset concentration. The required time for producing target gas concentration in storage chamber was exactly predicted by the model used in this study, and it required much longer time than the calculated time which divided the volume of chamber by flow rate. Therefore, for producing target gas concentration as quickly as possible, it needs to supply higher flow rate of gas during the initial stage of experiment when gas concentration in storage chamber has not reached at target value. It appeared that the developed system was very useful for C.A experiments. Because one could decide a desired flow rate by the prediction model, control flow rate freely and easily by changing pressure in the pressure-regulating chamber and the accuracy was high.