• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.96-98
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• 2006

Proper water management is vital to achieve high performance and durability of PEFC (Polymer Electrolyte Fuel Cell). The effects of the residual water from PEFC after purge in shut-down processes on GDL/MEAs were investigated with freeze/thaw cycles Freeze/thaw cycle tests were conducted with single cells which were designed from transparent acryl plates. Single cells which contain several amount of residual water were cycles from $80^{\circ}C$ to $-28^{\circ}C$. The resistance changes of the single cells which have various amount of residual water were evaluated by ac-impedance analysis with 24 times of freeze/thaw cycles. Also, after the freeze/thaw cycles, the property changes were characterized by visual methods such as SEM, EPMA. Though it was difficult to observe noticeable property changes in the visual characterizations, the resistance of cells dramatically increased with the amount of remained water.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.30-36
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• 2012

A scroll expander has been designed to produce a shaft power from a R134a Rankine cycle for electricity generation. Heat was supplied to the Rankine cycle through a heat exchanger, which received heat from another cycle of water. In the water cycle, water was heated up in a boiler using biogenic solid fuel. The designed scroll expander was a horizontal type, and a trochoidal oil pump was employed for oil supply to bearings and Oldham-ring keys. For axial compliance, a back pressure chamber was created on the backside of the orbiting scroll base plate. Numerical study has been carried out to estimate the performance of the designed scroll expander. The expander was estimated to produce the shaft power of about 2.9 kW from a heat supply of 36 kW, when the temperature of R134a was $80^{\circ}C$ and $35^{\circ}C$ at the evaporator and condenser of the Rankine cycle, respectively. The expander efficiency was about 70.5%. When the amount of heat supply varied in the ranges of 7.5~55 kW, the expander efficiency changed in the range of 45.6~70.5%, showing a peak efficiency of 70.5% at the design shaft speed.

• Journal of Korean Society of Water and Wastewater
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• v.36 no.2
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• pp.107-119
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• 2022

The frequent detection and occurrence of micropollutants (MPs) in aquatic ecosystems has raised public health concerns worldwide. In this study, the behavior of 50 MPs was investigated in three different domestic wastewater treatment plants (WWTPs). Furthermore, the Kruskal-Wallis test was used to assess the geographical and seasonal variation of MPs in the WWTPs. The results showed that the concentrations of 43 MPs ranged from less than 0.1 to 237.6 ㎍ L^-1, while other seven MPs including 17-ethynylestradiol, 17-estradiol, sulfathiazole, sulfamethazine, clofibric acid, simvastatin, and lovastatin were not detected in all WWTPs. Among the detected MPs, the pharmaceuticals such as metformin, acetaminophen, naproxen, and caffeine were prominent with maximum concentrations of 133.4, 237.6, 71.5, and 107.7 ㎍ L^-1, respectively. Most perfluorinated compounds and nitrosamines were found at trace levels of 1.2 to 55.3 ng L^-1, while the concentration of corrosion inhibitors, preservatives (parabens), and endocrine disruptors ranged from less than 0.1 to 4310.8 ng L^-1. Regardless of the type of biological treatment process such as MLE, A2O, and MBR, the majority of pharmaceuticals (except lincomycin, diclofenac, iopromide, and carbamazepine), parabens (except Methyl paraben), and endocrine disruptors were removed by more than 80%. However, the removal efficiencies of certain MPs such as atrazine, DEET, perfluorinated compounds (except PFHxA), nitrosamines, and corrosion inhibitors were relatively low or their concentration even increased after treatment. The results of statistical analysis reveal that there is no significant geographical difference in the removal efficacy of MPs, but there are temporal seasonal variations in all WWTPs.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1119-1124
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• 2006

The objectives of this paper are to investigate the performance of silica gel-water adsorption refrigeration system with heat recovery process from the system experiment. This system can be driven by waste heat at near ambient temperature from $60^{\circ}C$ to $90^{\circ}C$. The cooling capacity and coefficient of performance(COP) were measured from various experimental conditions. An experimental results revealed the influence of operating temperatures(hot, cooling and chilled water), water flow rates, and adsorption-desorption cycle times on cooling capacity and COP. Under the standard conditions of $80^{\circ}C$ hot water, $25^{\circ}C$ cooling water, $14^{\circ}C$ chilled water inlet temperatures and 420sec cycle time, a cooling capacity of 1.14kW and a COP for cooling of 0.55 can be achieved.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.216-216
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• 2015

Frequent hydro-meteorological events caused by global climate change and human exacerbate activities, make the water resource problem more complicated. The increasing speed urbanization brings a significant impact on the city flood control and security, water supply safety, water ecological security, water environment safety and the water engineering security in China, and puts forward higher requirements to urban water integrated management, undoubtedly which become the biggest obstacle for water ecological civilization construction, thus urgent requiring an advanced methods to enhance the effectiveness of the water integrated management. The other fields of smart ideas point out a development path for water resource development. The construction demand of smart water resource is expounded in the paper, combining the philosophy of modern Internet of things with the application of cloud computing technology. The concept of smart water resource is analyzed, the connotation characteristics of smart water resource is extracted, and the general model of smart water resource is refined. Then, the frame structure of smart water resource is put forward. The connotation and the overall framework of the smart water resource represent a higher level of water resource informationization development and provide a comprehensive scientific and technological support to transform water resource management from an extensive, passive, static, branch and traditional management to a fine, active, dynamic, collaborative and modern management.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.238.2-238.2
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• 2010

Recently, environmental pollution and energy depletion problems have been issued over the world. For this reason, many renewable systems have been developing. Of these, the Ocean Thermal Energy Conservation(OTEC) is drawing attention as the upcoming alternative energy source. In this paper, the efficiency of each of OTEC which harness the effluent from nuclear power plant was analyzed by using computer calculation. The result, shows that Ul-jin Nuclear Power Plant is the best place geographically and the regenerative cycle is most outstanding performance cycle for OTEC. The difference of temperature between surface water and deep water temperature should be greater than $20^{\circ}C$ in order to increase the efficiency.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2809-2818
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• 2022

In this investigation work, liquid-liquid extraction (L.L.E) through three distinctive frameworks have been examined for assurance of slip velocity (S.V), and characteristic velocity (C.V) in a non-center rotating column (N.C.R.C) with a wide extend of factors. Three double frameworks with distinctive interfacial tension comprising of toluene-water (high interfacial tension), n-butyl acetate-water (medium interfacial tension), and n-butanol-water (low interfacial tension) were investigated for tests. Two common relationships for the expectation of S.V and C.V, including phase stream rates, rotor speed, column geometry additionally physical properties, are displayed. The recommended relationships were compared with test information gotten from the writing and the display examination. Findings of this study, the present proposed correlations are more accurate than those previously reported.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.691-699
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• 2010

In recent years, increases in impervious areas with rapid urbanization and land use changes are causing numerous hydrologic cycle and environmental problems. Impermeable pavement have a various defect such as collection rainwater, decreasing of sliding resistance, and etc. In this study, the hydrologic cycle effect of permeable pavement were analyzed by the experiment and the numerical simulation. The numerical model used was a modified SWMM especially for considering the hydrologic cycle effect of permeable pavement. The parameters of modified SWMM were revised by the experimental results. Also, the effects of runoff quantity reduction are reviewed when permeable pavement is applied to Incheon Cheongna watershed. The hydrologic cycle analysis of Incheon Cheongna watershed, continuous simulations of urban runoff were performed. The analysis results of permeable pavement setup effect on runoff are follows: the surface runoff after permeable pavement setup decreases to 74.35% of the precipitation whereas the surface runoff before permeable pavement setup amounts to 81.38% of the precipitation; the infiltration after permeable pavement setup increases to 15.13% of the precipitation whereas the infiltration before permeable pavement setup amounts to 8.32% of the precipitation.

• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.517-523
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• 2006

The sustainable development is a key issue in the whole field of economy, culture and society, which can be accomplished by the improvement of environment. Recently, life cycle assessment(LCA) has been applied to reduce environmental impacts preliminarily by evaluating the environmental performance of a product through its life cycle. In this study, life cycle assessment was performed to analyze quantitatively the environmental impact on the interior panel of electric motor unit(EMU). As a result, the interior panel with aluminum showed the most global warming(GW), while that with phenol and plastic showed high fresh water aquatic ecotoxicity(FAET) and marine water aquatic ecotoxicity(MAET), respectively. Global warming was occurred mainly due to the emission of $CO_2$ by energy consumption. FAET and MAET were caused by the pollutants released from acid-washing and paints coating process. Therefore, an environmental-friendly EMU can be designed considering the environmental impacts of interior panel.

• Journal of the Korean Institute of Gas
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• v.3 no.1
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• pp.14-20
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• 1999

This study describes the results of Coefficient of Performance(COP) analysis by cycle simulation for two types of absorption-compression hybrid cycle using the Water/Lithium Bromide solution pair. These types are basic hybrid systems introducing a mechanical compression process into the refrigerant vapor phase of the single effect absorption cycle. In absorption-compression hybrid cycles, coefficient of performance is improved compared with absorption cycle. Hybrid cycle Type 2 is considered as a key technology to support energy utilization system, given its capability of utilizing waste heat to drive system with a high level of efficiency.