• Nuclear Engineering and Technology
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• v.18 no.2
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• pp.107-116
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• 1986

The steady and unsteady state models were established for the performance analysis and design of heavy water distillation columns packed with corrugated wire mesh. After the steady state model was derived with pressure drops, separated D$_2$O concentration and temperature profiles and pressure gradients in the column were obtained by solving MESH equations with equation tearing method. For the analysis of unsteady state behavior, the equilibrium stage transient model deduced from modifying the Cohen's ideal cascade equation was used to predict the concentration change of heavy water with time. These models were in good agreement with the experimental results of heavy water distillation at total reflux. And the newly developed packing material turned out to be very efficient separation device for very small HETP, pressure drop and holdup.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.141-153
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• 2022

In this study, a numerical model of debris flow considering driftwood and entrainment erosion is developed. Subsequently, numerical simulations based on the observation data of the 2011 Mt. Umyeon are performed. To develop the debris flow model, the Nays2DFlood model, which is a flooding model based on the shallow water equation, is coupled with the transport diffusion of mixed sediment concentration, debris flow bottom shear stress, and entrainment erosion modules. The simulation closely reproduced the depth, flow velocity, and debris flow volume of Mt. Umyeon. In addition, the reproducibility of the simulation result with driftwood is more accurate than that without driftwood. The results of this study can facilitate in establishing measures to reduce debris disasters, thus alleviating the current increase in debris damage due to climate change.

• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.38-43
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• 2012

The purpose of this study is to carry out the consequence analysis of an accident related to the release of Hydrogen chloride occurred in a petrochemical company in Korea and suggest the measures to prevent similar accidents from happening again. The total amount released through the safety valve of HCl Column was calculated based on the rated capacity of the safety valve, the ideal gas equation and mechanical energy balance, respectively. As a result of the calculation, we found that the amount of HCl released through the safety valve was at least 76.8 kg. Also, we predicted the dispersion concentration at the position of the injured workers(more than 350 m away from the accident location) using simulation programs such as PHAST. The results of ALOHA and K-CARM are 304 ppm and 1,700 ppm respectively. However, PHAST calculation indicated that the concentration is less than l ppm. From these results, we can understand that workers were injured by HCl gas released from the safe valve and the concentration of gas might be less than 1 ppm. Also, it is important for toxic gases such as HCl to be vented safely to the atmosphere after scrubbing.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.530-537
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• 2014

Moisture is a major factor causing the deteriorative physical change, microbial growth, and chemical reaction of the products. In this study, the moisture absorbing composite films have been prepared with moisture absorbing material of polyacrylic acid partial sodium salt (PAPSS) impregnated on LLDPE polymer for the functional packaging applications. The results showed that PAPSS impregnated film illustrated uniformly dispersed PAPSS particles in the LLDPE polymer matrix. The transparency of the PAPSS impregnated film decreased slightly at higher PAPSS concentrations. An increase in the PAPSS content for moisture-absorbing films showed a similar decrease in tensile strength, percent elongation at break, and tear strength. Their values of films impregnated with PAPSS of 0.5, 1, and 2% showed no significant difference. Meanwhile, 4% PAPSS films significantly decreased the values of mechanical properties compared to the films impregnated with different PAPSS levels. Values of the oxygen permeability and water vapor permeability for PAPSS impregnated films decreased significantly with greater PAPSS. The results indicate that 4% PAPSS impregnated in LLDPE films had high affinity of moisture absorbencies compared to the other films. The mathematical equation that best described the moisture sorption isotherm of each film sample was the GAB equation at $25^{\circ}C$. The crystallization and melting temperatures of PAPSS films were influenced by the addition of PAPSS material, but showed good thermal stability.

• Membrane Journal
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• v.24 no.3
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• pp.223-230
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• 2014

A numerical analysis was performed for concentration of methane from the biogas using a polysulfone hollow fiber membrane permeator. Governing equations were derived for the countercurrent flow and numerically solved by using the Compaq Visual Fortran 6.6 software. When the methane mole fraction of feed was 0.5, the mole fraction of retentate increased from 0.5 to 0.8; the normalized retentate flow rate to the feed flow rate decreased from 1.0 to 0.57 at the given typical operating condition as the feed gas flowed from the inlet to the outlet of the membrane. As the methane mole fraction of feed was changed to 0.9, the methane mole fraction of retentate became 0.93 and the normalized retentate flow rate was changed to 0.91. When the pressure ratio of the permeate to the feed was varied from 0.33 to 0.17, there was a little difference in the methane mole fraction of retentate for the low stage cut of 0.1, whereas there was an significant increment for the high stage cut of 0.3. The retentate methane mole fraction remained relatively high despite the change of a stage cut as the area of the membrane increased from $1.14m^2$ to $2.57m^2$.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.2
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• pp.20-30
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• 1999

To improve water quality particularly for sea bathers along the Fylde coastal zone near Blackpool, North West England, waste water from a sewage outfall is studied using a mathematical model. The explicit second order accurate central scheme and the third order accurate QUICKEST scheme are used to represent the diffusion terms and the advection terms of the advective-diffusion equation, respectively. Hydrodynamic model is run for a coarse and fine grid, of 1km and 200m, respectively, obtaining good agreement with measured data. Water quality model is then used to predict faecal coliform levels in the region for four different scenarios, including discharges from: - (i) Fleetwood outfall, (ii)River Ribble for summer condition, (iii)River Ribble for winter condition, and (iv)combined sewer overflows for the Blackpool and Fleetwood communities. Main findings from the simulations are:- (i) Fleetwood outfall has a negligible impact on the beaches with respect to pathogen levels; (ii) Discharge from River Ribble for both summer and winter conditions is predicted in the range of coliform levels 10 -500 counts/100ml along the beach at Lytham St. Annes; and (iii) The CSO effluent discharges are predicted not to advect out into offshore by stronger tidal currents.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.59-66
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• 2012

The purpose of this study is to estimate the behavior and the mechanism of debris flow on the slope, which has specially various gradient plane. The numerical simulation was performed by using the Finite Differential Element method (FDM) based on the equation for the mass conservation and momentum conservation. The mechanism of flow type for debris flow is divided into three flow types which are stony debris flow, immature debris flow, and turbulent water flow, respectively. First, flow discharge, water flow depth, sediment volume concentration was investigated by variable input of flow discharge at the straight slope angle and two step inclined plane. As the input of flow discharge was decrease, flow discharge and water flow depth was increased, after the first coming debris flow only reached at the downstream. As the input of flow discharge was increased, the curve of flow discharge and flow depth was highly fluctuated. As the results of RMS ratio, the flow discharge and flow depth was lower two step slope angle than the straight slope angle. Second, the behavior of debris flow was investigated by the four cases of gradient degree at the downstream of slope angle. The band width of flow discharge and flow depth for $14^{\circ}$ between $16^{\circ}$ was higher than other gradient degree, and fluctuation curve was continuously high after 10 seconds.

• Journal of agriculture & life science
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• v.45 no.2
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• pp.35-41
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• 2011

This study was carried out to investigate the relation of acid depositions and chlorophyll concentration in the Pinus thunbergii leaves. pH of throughfall in Pinus thunbergii forest was 4.20 at industrial sites, and 4.87 at urban sites. Total chlorophyll concentration in leaves were 0.5984 at industrial sites, and 0.6784 at urban sites. The average $SO_2$ concentration in air was 0.029ppm at industrial sites, and 0.011ppm at urban sites. Correlation between chlorophyll concentration in the Pinus thunbergii leaves and acid depositions was pH (r=-0.8769), ${NO_3}^-$ (r=0.6983), ${SO_4}^{2-}$ (r=0.8929), $SO_2$ (r=0.8738), and $NO_2$ (r=0.8523) (p<0.001). respectively. The estimation equation of chlorophyll concentration in the Pinus thunbergii leaf (Y) were given by Y=4.8979 + 0.7698pH + $0.8412{SO_4}^2$ + $0.8673SO_2$, + $0.8767NO_2$+ $0.8767{NO_3}^-$ ($r^2$=0.8873), which coefficients of determination was 0.88.

• Journal of Environmental Impact Assessment
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• v.29 no.6
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• pp.403-413
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• 2020

A mathematical model comprised with eight simultaneous quasi-linear partial differential equations was suggested to provide optimal chlorination strategy. Upstream weighted finite element method was employed to construct multidimensional numerical code. The code was verified against measured concentrations in three type of reactors. Boundary conditions and reaction rate were calibrated for the sixteen cases of experimental results to regenerate the measured values. Eight reaction rate coefficients were estimated from the modeling result. The reaction rate coefficients were expressed in terms of pH and temperature. Automatic optimal algorithm was invented to estimate the reaction rate coefficients by minimizing the sum of squares of the numerical errors and combined with the model. In order to minimize the concentration of chlorine and pollutants at the final usage sites, a real-time predictive control system is imperative which can predict the water quality variables from the chlorine disinfection process at the water purification plant to the customer by means of a model and operate the disinfection process according to the influent water quality. This model can be used to build such a system in water treatment plants.