• Nuclear Engineering and Technology
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• 제34권4호
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• pp.286-300
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• 2002

An algorithm for the sodium boiling model has been developed for calculation of the void reactivity feedback as well as the fuel and cladding temperatures in the KALIMER core after onset of sodium boiling. Modeling of sodium boiling in liquid metal reactors using sodium as a coolant is necessary because of phenomenon difference comparing with that observed generally in light water reactor systems. The applied model to the algorithm is the multiple-bubble slug ejection model. It allows a finite number of bubbles in a channel at any time. Voiding is assumed to result from formation of bubbies that (ill the whole cross section of the coolant channel except for the liquid film left on the cladding surface. The vapor pressure, currently, is assumed to be uniform within a bubble The present study is focused on not only demonstration of the vapor bubble behavior predicted by the developed model, but also confirmation of a qualitative acceptance for the model. As a result, the model can represent important phenomena in the sodium boiling, but it is found that further effort is also needed for its completition.

• Proceedings of the KSME Conference
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• 대한기계학회 2003년도 추계학술대회
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• pp.1-6
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• 2003

The purpose of the present study is to investigate the capillary heat transportation limitation in heat pipe according to the change of screen mesh wick porosity. Diameter of pipe was 6 mm, and mesh numbers are 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of wick porosity and mesh number, the capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, and capillary heat transportation limitation are analyzed by theoretical design method of a heat pipe. As some results, the capillary heat transportation limitation in screen mesh wick heat pipe is largely affected by wick porosity and mesh number.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.235-239
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• 1998

Ultrafine $SnO_2$ powder was prepared by the diffusion mixing gas-phase reaction of $SnCl_4$(g) and water vapor. The effects of reaction variables, such as the chloride partial pressure, the reaction temperature, and the residence time is the reactor, on the powder size were examined systematically. Calculated concentration and distribution of chemical species, using the Burke-Schumann diffusion mixing model, were compared with the experimetal results. The effects of the reaction variables on the powder size were also discussed qualitatively.

• Proceedings of the Korean Society of Crop Science Conference
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• 한국작물학회 2005년도 국제학술회의
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• pp.198-199
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• 2005

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 한국농림기상학회 2003년도 춘계 학술발표논문집
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• pp.50-53
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• 2003

Models have been developed to estimate leaf wetness duration (LWD) using conventional weather observations, e.g., air temperature, water vapor pressure, and wind speed, which are relatively invariant over space (Pedro and Gillespie, 1982; Gleason et al., 1994; Francl and Panigrahi, 1997).(omitted)

• Journal of Bio-Environment Control
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• 제10권4호
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• pp.232-236
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• 2001

Four air temperature levels of 23, 25, 27 and 29$^{\circ}C$, three humidity levels of 85, 90 and 95% R.H. at photosynthetic photon flux (PPF) of 50 $\mu$mol.m$^{-2}$ .s$^{-1}$ were provided to investigate the effect of vapor pressure deficit on the evapotranspiration rate (EVTR) and graft-taking of watermelon grafted seed-increase. Thus EVTR of grafted seedlings increased with increasing air temperature at high humidity of 95%R.H. At relatively low humidity of 85% R.H., grafted seedlings showed a high EVTR and some wilting of scions was observed at this condition. This result would be ascribed to the low supply of water to vascular bundles according to the insufficient joining of scions and rootstocks. Differences in EVTR between 90% R.H. and 95% R.H. were not observed. Grafted seedlings showed high graft-taking at high relative humidity. Relative humidity had highly influenced to the graft-taking as compared to the air temperature. Graft-taking increased with decreasing vapor pressure deficit. Graft-taking greater than 90% was found at vapor pressure deficit less than 0.4kPa which could be obtained at humidity higher than 90% R.H. Therefore it is required to control the humidity higher than 90% R.H. for suppressing EVTR of grafted seedlings and preventing some wilting of scoins and thus enhancing the graft-taking of grafted seedlings.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.477-480
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• 2007

Hydrate phase equilibrium for the binary CO2+water and CH4+water mixtures in silica gel pore of nominal 6, 30, and 100 nm were measured and compared with the cacluated results based on van der Waals and Platteeuw model. At a specific temperature three-phase hydrate-water-vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher-pressure condition depending on pore sizes when compared with those of bulk hydrates. Notably, hydrate phase equilibria for the case of 100 nominal urn pore size were nealy identical with those of bulk hydrates. The activities of water in porous silica gels were modified to account for capillary effect, and the calculation results were generally in good agreement with the experimental data.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.41-47
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• 2002

A model of simultaneous heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled vertical plate absorber was developed. The model can predict temperature and concentration profiles as well as the absorption heat and mass fluxes, the total heat and mass transfer rates and the heat and mass transfer coefficients. Besides, the effect of operating condition on absorption mass flux has been investigated, with the result that the absorption mass flux is increased as the inlet cooling water temperature decreases, the system pressure increases and the inlet solution concentration increases. And among the effects of operating parameters on absorption mass flux, the effect of inlet solution concentration is dominant.

• New & Renewable Energy
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• 제3권2호
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• pp.47-52
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• 2007

Hydrate phase equilibrium for the binary $CO_{2}$+water and $CH_{4}$+water mixtures in silica gel pore of nominal 6, 30, and 100 nm were measured and compared with the cacluated results based on van der Waals and Platteeuw model. At a specific temperature three-phase hydrate-water-vapor (HLV) equilibrium curves for pore hydrates were shifted to the higher-pressure condition depending on pore sizes when compared with those of bulk hydrates. Notably, hydrate phase equilibria for the case of 100 nominal nm pore size were nearly identical with those of bulk hydrates. The activities of water in porous silica gels were modified to account for capillary effect, and the calculation results were generally in good agreement with the experimental data.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.230-236
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• 2021

Ionic conduction mechanism of Mg-Al layered double hydroxides (LDHs) intercalated with CO₃^2- (Mg-Al CO₃^2- LDH) was studied. The electromotive force for the water vapor concentration cell using Mg-Al CO₃^2- LDH as electrolyte showed water vapor partial pressure dependence and obeyed the Nernst equation, indicating that the hydroxide ion transport number of Mg-Al CO₃^2- LDH is almost unity. The ionic conductivity of Mg(OH)₂, MgCO₃ and Al₂(CO₃)₃ was also examined. Only Al₂(CO₃)₃ showed high hydroxide ion conductivity of the order of 10^-4 S cm^-1 under 80% relative humidity, suggesting that Al₂(CO₃)₃ is an ion conducting material and related to the generation of carrier by interaction with water. To discuss the ionic conduction mechanism, Mg-Al CO₃^2- LDH having deuterium water as interlayer water (Mg-Al CO₃^2- LDH(D₂O)) was prepared. After the adsorbed water molecules on the surface of Mg-Al CO₃^2- LDH(D₂O) were removed by drying, DC polarization test for dried Mg-Al CO₃^2- LDH(D₂O) was examined. The absorbance attributed to O-D-stretching band for Mg-Al CO₃^2- LDH(D₂O) powder at around the positively charged electrode is larger than that before polarization, indicating that the interlayer in Mg-Al CO₃^2- LDH is a hydroxide ion conduction channel.