• Journal of environmental and Sanitary engineering
• /
• v.16 no.2
• /
• pp.38-46
• /
• 2001

In this work, the heterogeneous ion exchange membrane was used in a electrodialysis apparatus to treat a Ni planting rinse water because the heterogeneous ion exchange membrane was excellent efficiency as compared with low manufacturing cost, was easy to make, and had a good mechanical properties. For a regeneration of membrane and to obtain the optimal condition for a scale-up of apparatus after treating Ni plating rinse water, we would find about the limiting current density and the concentration polarization. When the Ni plating rinse water 150mg/L was treated with the electrodialysis apparatus using the heterogeneous ion exchange membrane, the limiting current density was about $1.49{\;}mA/\textrm{cm}^2$. And the limiting current density increased with the flow rate and concentration of Ni plating rinse water. We recognized that the used membrane could be reused by periodic backwashing because efficiency was constant when the membrane was backwashed after treating wastewater.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.452-455
• /
• 2007

The geothermal heat pump system is designed for cooling and heating for three stories building (2,435 $m^2$) includes total 79 heat pumps. Therefore, the monitoring system is installed for each floor and the data is automatically transmitted to the monitoring system. Heat exchange rate and temperature of a geothermal heat pump system have been monitored for a long period. The seasonal operation of geothermal heat pump shows the different shape of heat exchange rate for cooling and heating. Ground water flow can influence on heat exchange rate and thermal storage of the system. In order to define the hydraulic characteristics and groundwater temperature variation, the relationships among air temperatures, groundwater temperatures, water table, and precipitation are analysed.

• Korean Journal of Computational Design and Engineering
• /
• v.17 no.1
• /
• pp.54-61
• /
• 2012

In this paper, we performed numerical analysis to improve the heat exchange efficiency of wasted heat recovery ventilator which has a delivery and a exhaustion fan. One of the most important design factors that affect the efficiency of heat exchange is uniform counter-flow between inbound and outbound air flows. We had simulated several types of porous plates which were installed at air intake area. With plate having 45 degrees of installation angle and 15 mm diameter holes which are uniformly arranged, we can generate a uniform air flows at the area of porous media where inbound and outbound air flows are cross over. In addition, we installed a duct to reduce vortex flows at the outlet and to discharge exhaust airs rapidly. By using the proposed numerical assessment, we expect the improvement of the heat exchange efficiency of ventilator.

• Nuclear Engineering and Technology
• /
• v.53 no.8
• /
• pp.2761-2766
• /
• 2021

A method for preparing "reagent" for radioactive methyliodide vapors production using an isotopic exchange reaction has been developed. Based on the obtained data of the isotopic exchange efficiency and hydraulic resistance, white fused alumina (700-840 ㎛) was selected as the carrying agent material for "reagent" production. The radioiodine isotopic exchange dependences on such parameters as temperature, gas flow velocity, and the methyliodide concentration in it were determined. Optimal conditions have been selected to achieve 85% of the isotopic exchange rate in 1 h of the experiment. The obtained data allowed to develop an approach to the test of iodine filters for nuclear power plants and to determine their efficiency.

• Journal of the Korean Electrochemical Society
• /
• v.9 no.4
• /
• pp.170-177
• /
• 2006

Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.13 no.2
• /
• pp.109-121
• /
• 2001

This paper describes results of an experimental study to examine the effect of a submerged horizontal breakwater to sea water exchange. Flow measurements were taken by using a PIV(Particie Image Velocimetry) system, and mean currents and wave ellipses extracted through the harmonic analysis are presented. As results, the rates of circulating flow were closely connected with the volume flux of incident waves and the counter-rotating vortex pair was observed at the onshore side of a plate. The dye study showed that incoming sea water and polluted water body mixed up significantly due to turbulent motions induced by a jet-like flow.

• Nuclear Engineering and Technology
• /
• v.33 no.1
• /
• pp.83-92
• /
• 2001

The properties of off-gas generated from vitrification process of ion-exchange resin were characterized. Theoretical composition and flow rate of the off-gas were calculated based on chemical composition of resin and it＇s burning condition inside CCM. The calculated off-gas flow rate was 67.9Nm$^3$/h at the burning rate of 40kg/h. And the composition of off-gas was avaluated as $CO_2$(41.4%), steam(40.0%), $O_2$(13.3%), NO(3.6%), and SO$_2$(1.6%) in order. Then, actual flow rate and composition of off-gas were measured during pilot-scale demonstration tests and the results were compared with theoretical values. The actual flow rate of off-gas was about 1.6 times higher than theoretical one. The difference between theoretical and actual flow rates was caused by the in-leakage of air to the system, and the in-leakage rate was evaluated as 36.3Nm$^3$/h. Because of continuous change in the combustion parameters inside CCM, during demonstration tests, the concentration of toxic gases showed wide fluctuation. However, the concentration of CO, a barometer of incompleteness of combustion inside CCM, was stabilized soon. The result showed quasi-equilibrium state was achieved two hours after feeding of resin.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.1
• /
• pp.74-85
• /
• 2016

For the assessment of seawater exchange rates in Danghangpo bay, Dangdong bay, Wonmun bay, Gohyunsung bay, and Masan bay, which are small-scale inner bays of Jinhae bay, an EFDC model was used to reproduce the seawater flow of the entire Jinhae bay, and Lagrange (particle tracking) and Euler (dye diffusion) model techniques were used to calculate the seawater exchange rates for each of the bays. The seawater exchange rate obtained using the particle tracking method was the highest, at 60.84%, in Danghangpo bay, and the lowest, at 30.50%, in Masan bay. The seawater exchange rate calculated based on the dye diffusion method was the highest, at 45.40%, in Danghangpo bay, and the lowest, at 34.65%, in Masan bay. The sweater exchange rate was found to be the highest in Danghangpo bay likely because of a high flow velocity owing to the narrow entrance of the bay; and in the case of particle tracking method, the morphological characteristics of the particles affected the results, since once the particles get out, it is difficult for them to get back in. Meanwhile, in the case of the Lagrange method, when the particles flow back in by the flood current after escaping the ebb current, they flow back in intact. However, when a dye flows back in after escaping the bay, it becomes diluted by the open sea water. Thus, the seawater exchange rate calculated based on the dye diffusion method turned out to be higher in general, and even if a comparison of the sweater exchange rates calculated through two methods was conducted under the same condition, the results were completely different. Thus, when assessing the seawater exchange rate, more reasonable results could be obtained by either combining the two methods or selecting a modeling technique after giving sufficiently consideration to the purpose of the study and the characteristics of the coastal area. Meanwhile, through a comparison of the degree of closure and seawater exchange rates calculated through Lagrange and Euler methods, it was found that the seawater exchange rate was higher for a higher degree of closure, regardless of the numerical model technique. Thus, it was deemed that the degree of closure would be inappropriate to be used as an index for the closeness of the bay, and some modifications as well as supplementary information would be necessary in this regard.

• Membrane Journal
• /
• v.27 no.5
• /
• pp.406-414
• /
• 2017

In this study, we have developed pore-filled ion-exchange membranes (PFIEMs) filled with ionomer in a thin polyethylene porous film (thickness = $25{\mu}m$) and investigated the charge-discharge characteristics of the all vanadium redox flow battery (VRFB) employing them. Especially, the degree of crosslinking and free volume of the PFIEMs were appropriately controlled to produce ion-exchange membranes exhibiting both the low membrane resistance and low vanadium permeability by mixing crosslinking agents having different molecular size. As a result, the prepared PFIEMs exhibited excellent electrochemical properties which are comparable to those of the commercial membranes. Also, it was confirmed through the experiments of vanadium ion permeability and VRFB performance evaluation that the PFIEMs showed low vanadium ion permeability and high charge-discharge efficiency in comparison with the commercial membrane despite their thin film thickness.

• Journal of Korean Society on Water Environment
• /
• v.29 no.6
• /
• pp.777-781
• /
• 2013

Ion-exchange technology is one of the best for removing nitrate from drinking water. However, problems related to the disposal of spent brine from regeneration of exhausted resins must be overcome so that ion exchange can be applied more widely and economically, especially in small communities. In this background, a combined bio-regeneration and ion-exchange system was operated in order to prove that nitrate-laden resins could be bio-regenerated through direct contact with denitrifying bacteria. A nitrate-selective A520E resin was successfully regenerated by denitrifying bacteria. The bio-regeneration efficiency of nitrate-laden resins increased with the amount of flow passed through the ion-exchange column. When the fully exhausted resin was bio-regenerated for 5 days at the flowrate of 30 BV/hr and MLSS concentration of $125{\pm}25mg/L$, 97.5% of ion-exchange capacity was recovered. Measurement of nitrate concentrations in the column effluents also revealed that less than 5% of nitrate was eluted from the resin during 5 days of bio-regeneration. This result indicates that the main mechanism of bio-regeneration is the direct reduction of nitrate by denitrifying bacteria on the resin.