• Nuclear Engineering and Technology
• /
• 제35권2호
• /
• pp.171-177
• /
• 2003

A dynamic compartment model was required for the prediction of radiological consequences of the tritiated vapor released from the nuclear facility after an accident. A computer code, ECOREA-T, was developed by incorporating the unit models for the evaluation of tritium behavior in the environment. Dry deposition of tritiated vapor from the atmosphere to the soil was calculated using a deposition velocity. Transport of tritium from the atmosphere to the plant was calculated using a specific activity model, and the result was compared with the Belot's analytic solution. Root uptake of tritiated water from the soil and formation of OBT from T were considered in the model. The ECOREA-T code was verified by comparing the results from the other computer codes using a scenario developed through BIOMOVS II study. The results showed good agreements.

• 한국유체기계학회 논문집
• /
• 제18권6호
• /
• pp.76-80
• /
• 2015

The purpose of this study is to understand the cavitation phenomena in centrifugal pumps through computational fluid dynamics method. NPSH characteristic curve is measured from different flow operating conditions. Steady state, liquid-vapor homogeneous method with two equations transport turbulence model is employed to estimate the NPSH curve in centrifugal pumps. The Rayleigh-Plesset cavitation model is adapted as source term for inter-phase mass transfer in order to understand cavitation phenomena in centrifugal pumps. The cavitation incipient curve is clearly estimated at different flows operating conditions. A relationship is made between cavitation incipient and NPSH curve. Also the effects on water vapor volume fraction and pressure load distributions on the impeller blade are also described.

• 대한기계학회논문집B
• /
• 제24권11호
• /
• pp.1428-1436
• /
• 2000

The absorption of vapor involves simultaneous heat and mass transfer in the vapor/liquid system. In this paper, a numerical study for vapor absorption process into LIBr-H$_2$O solution film flowing over helical absorber has been carried out. Axisymmetric cylindrical coordinate system was adopted to model the helical tube and the transport equations were solved by the finite volume method. The effects of operating conditions, such as the cooling water temperature. the system pressure, the film Reynolds number and the solution inlet concentration have been investigated in view of the absorption mass flux and the total absorption mass flux and the total absorption rate. The results for the temperature and concentration profiles, as well as the local absorption mass flux at the helical absorber are presented. It is shown that solution inlet concentration affected other than operation conditions for a mass flux.

• Environmental Engineering Research
• /
• 제25권3호
• /
• pp.281-289
• /
• 2020

Environmental fate of ionizable organic pollutants such as perfluoroalkyl acids (PFAAs) are of increasing interest but has not been well understood because of uncertain values for parameters related with atmospheric interphase partitioning behavior. In the present study, not only the values for air-water partition coefficient (K_AW) and dissociation constant (pKa) of PFAAs were induced by adjusting to in situ measurements of air-water distribution coefficient between vapor phase and rainwater but also gas-particle partition coefficients were also estimated using three-phase partitioning model of ionizable organic pollutants, in situ measurements of PFAAs in aerosol and air vapor phase, and obtained parameter values. The pKa values of PFAAs we obtained were close to the minimum values suggested in literature except for perfluorooctane sulfonic acids, and COSMOtherm-modeled K_AW values were assessed to more appropriate among suggested values. When applying parameter values we obtained, it was predicted that air particle-associated fate and transport of PFAAs could be negligible and PFAAs could distribute ubiquitously along the transection from urban to rural region by pH-dependent phase transfer in air. Our study is expected to have some implications in prediction of the environmental redistribution of other ionizable organic compounds.

• 한국대기환경학회지
• /
• 제29권1호
• /
• pp.64-73
• /
• 2013

Because some particulate matter emission sources may inherently produce soluble species, or some soluble species may be produced during atmospheric transport, it is important to understand the origin of a particles's solubility when water-soluble tracers are used in source apportionment studies. Laboratory experiments were performed on three types of soils (Mongolia grassland, Mongolia desert, and Korean rural soils), to study the impact of acidification by nitric acid vapor on the solubility of metals in the soils. To achieve this goal, concentrations of water-soluble metals (Na, Mg, Al, K, Ca, Mn, and Fe) in the soils measured before and after acidification. Contributions of concentrations of water-soluble metal species before and after acidification attack to their total concentrations varied little with soil type. Concentrations of water-soluble Mg, Al, K, Ca, Mn, and Fe from the soils after interaction with nitric acid vapor increased, with significant increases in soluble Ca and Mn for all soil types suggesting soil acidification enhances the amount of leachable metal species in soil dust. There was little increase in water-soluble Na and K after acidification for each soil type. This experiment demonstrates that quantities of water-soluble metal species in particulate matter are produced under high gaseous nitric acid conditions.

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

• International Journal of Air-Conditioning and Refrigeration
• /
• 제6권
• /
• pp.45-55
• /
• 1998

A theoretical and experimental study is performed to investigate the characteristics of ice slurry product. By diffusion-controlled evaporation model the possibility of ice slurry is theoretically anticipated. The water vapor evaporated from the surface of droplets is extracted continuously from the chamber by a vacuum pump. The droplet diameter is measured by silicon immersion method. The ice slurry is obtained by spraying droplets of ethylene glycol aqueous solution in the chamber where pressure is maintained under the triple point of water. The droplet with the diameter of 300 $\mu\textrm{m}$and the initial temperature of 2$0^{\circ}C$ was changed into ice particle within the chamber of 1.33m in height.

• 설비공학논문집
• /
• 제9권2호
• /
• pp.134-143
• /
• 1997

A theoretical and experimental study has been performed to investigate the characteristics of ice-slurry product. By diffusion-controlled model, the possibility of ice slurry has been theoretically anticipated. The water vapor evaporated from the surface of droplets is extracted continuously from the chamber by a vacuum pump. The droplet diameter was measured by silion immersed method. The ice slurry has been obtained by spraying droplets of ethylene-glycol aqueous solution in the chamber where pressure is maintained under the triple point of water. The droplet of which the diameter is $300{\mu}m$, and the initial temperature is $20^{\circ}C$, was changed into ice particle within the chamber of which the height is 1.33m.

• 한국의류학회지
• /
• 제19권1호
• /
• pp.36-50
• /
• 1995

The purpose of this study was 1) to estimate the improvement of thermal storage/release and moisture transport properties of PEG-treated acrylic athletic socks and suggest the optimum add-on for PEG treatment, 2) to investigate wear performance of untreated cocks and two kinds of socks treated with PEG of minimum and optimum add-on respectively, and 3) to consider the effect of thermal storage/release and moisture transport properties of PEG- treated socks on the wear performance and the subjective comfort zone. Thermal activities of specimens treated by PDC were evaluated on a DSC by measuring the heat of fusion on heating and the heat of crystallization on cooling. Moisture regain, absorption speed, wickability, water retenti on value, and water-vapor permeability were measured. In the wear trials that the subjects performed a subsequent exercise protocol wearing three differently treated socks in a conditioned environment ($14\pm2^{\circ}C$, 65$\pm$2% R.H.), microclimate temperature and humidity, and subjective wear sensations including thermal sensation, wettedness, softness, fit, and overall comfort were obtained. PEC-treated specimens with more than 20% add-on showed thermal storage on heating and thermal release on cooling by a DSC and the heat contents of treated ones were generally proportional to the add-ons. Moisture transport properties were highly improved after PEG treatment and increased rapidly with increasing add-on. The tendencies were, however, relaxed above 50% add-on and the treated knits were much stiffer above that add-on. In the wear trials of untreated, PEG add-on 20%, and 50% acrylic socks, the changes of microclimate temperature of 50% socks were significantly less than that of 20% socks. PEG add-on 50% socks showed significantly less changes of microclimate humidity than other two kinds of socks. Three kinds of socks showed significant differences in overall comfort and add-on 50% socks were accepted more comfortable than other two kinds of socks. Comfort zone of foot was extended after PEG treatment on socks and it implied that the subjects wearing PEG- treated socks felt comfortable in wider ranges of microclimate temperature and humidity.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2002년도 춘계 국제 학술대회
• /
• pp.9-12
• /
• 2002

Diffusive transport of volatile organic compounds(VOCs) and their degradation by bacteria in unsaturated soils are couple by poorly understood mass transfer kinetics at the gas/water interface. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interaction in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations form diffusion experiments using toluene as a representative VOC in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas Putida, as the sole active microbial species. The coefficient for gas-liquid mass-transfer, K$\sub$LA/, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.