• 상하수도학회지
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• 제34권5호
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• pp.345-356
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• 2020

The removal of organic carbon and nutrients (i.e. N and P) from wastewater is essential for the protection of the water environment. Especially, nitrogen compounds cause eutrophication in the water environment, resulting in bad water quality. Conventional nitrogen removal systems require high aeration costs and additional organic carbon. Microbial electrochemical system (MES) is a sustainable environmental system that treats wastewater and produces energy or valuable chemicals by using microbial electrochemical reaction. Innovative and cost-effective nitrogen removal is feasible by using MESs and increasing attention has been given to the MES development. In this review, recent trends of MESs for nitrogen removal and their mechanism were conclusively reviewed and future research outlooks were also introduced.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.136-147
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• 2015

Dead-ended operation of Proton Exchange Membrane Fuel Cell(PEMFC) provides the simplification of fuel cell systems to reduce fuel consumption and weight of fuel cell. However, the water accumulation within the channel prohibits a uniform supply of fuel. Optimization of the purge strategy is required to increase the fuel cell efficiency since fuel and water are removed during the purge process. In this study, we investigated the average voltage output which depends on two interrelated conditions, namely, the supply gas pressure, purging valve open time. In addition, flow visualization was performed to better understand the water build-up on the anode side and cathode side of PEMFC in terms of a variety of the current density. We analyzed the correlation between the purge condition and water flooding.

• 한국정밀공학회지
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• 제33권1호
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• pp.45-51
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• 2016

The present study uses an electron beam (e-beam) to modify the wetting characteristics of thermoplastic polymer surfaces. A high energy e-beam irradiated various polymer surfaces (PET, PMMA, and PC), with variations in irradiation time and applied current. The water contact angles were measured on the e-beam irradiated surfaces in order to investigate the changes in the surface energy and the relevant wettability. Furthermore, XPS analyses were performed to investigate the chemical composition change in the e-beam irradiated surfaces; the results showed that the hydrophilic groups (C-O) increased after the electron beam irradiation. Also, water collection tests were performed for various polymer samples in order to investigate the effect of the surface energy on the ability of water collection, from which it can be seen that the irradiated surfaces revealed better water-collecting capability than pure polymer surfaces.

• 한국물환경학회지
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• 제29권1호
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• pp.127-137
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• 2013

Reuse of wastewater will intensify in the coming decades due to water shortage, the change of climatic conditions, the need for industrial and agricultural use and the necessity of improving health and environmental conditions for the growing population. This paper considers (a) the status and trends of wastewater reuse and reclamation in the world, (b) case studies of wastewater reuse projects, (c) analysis of technology level, (d) forecast of global market, and (e) the future views and directions in development of wastewater reuse technologies. Based on the available documented literature, this paper provides a review assessment of the current status of the wastewater treatment processes including potential applications for reuse. Key challenges for both wastewater treatment and reuse are also discussed in the paper and include recommendations, e.g. cost, effluent water quality, energy use and technical solutions, for future developments.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.171-181
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• 2007

Blending effects of hydrogen and water vapor on flame structure and NOx emission behavior are numerically studied with detailed chemistry in methane-air counterflow diffusion flames. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuels of methane-hydrogen-water vapor through the molar addition of $H_2O$. Flame structure is changed considerably for hydrogen-blending methane flames and hydrogen-blending methane flames diluted with water vapor in comparison to pure methane flame. These complicated changes of flame structures also affect NOx emission behavior considerably. The changes of thermal NO and Fenimore NO are analyzed for various combinations of the fuel composition. Importantly contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, hydrogen-blending methane flames, and hydrogen-blending methane flames diluted with water vapor.

• Nuclear Engineering and Technology
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• 제33권2호
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• pp.145-155
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• 2001

This simulation first allows us to define a transition zone from a bubble to jet mode of the argon out-flow and hereinafter to define a similar area for water-steam leak in the KALIMER SG (Korea Advanced Liquid Metal Reactor Steam Generator) using a water mock-up system, taking into account the KALIMER leak classification and tube bundle design, as a simulation of a real water-steam into sodium leak. in accordance with leak conditions in the KALIMER SG, the transition from bubbling to jetting is studied by means of turbulence regime simulation for argon out-flow through a very small orifice, which has the equivalent diameter of about 0.253 mm. finally the noise generation mechanism is explained from the existing experimental data. We also confirmed the possibility of micro-leak detection from the information of the bubbling mode through simulations and the experiment in this study.

• 한국태양에너지학회 논문집
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• 제29권4호
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• pp.34-40
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• 2009

$1m^3$ hydrate of pure methane can be decomposed to the maximum of $216m^3$ methane at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore, the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18-24% less than the liquefied transportation. In the present investigation, experiments and theoretical calculation carried out for the formation of methane hydrate in NaCl 3.5wt% solution. The results show that the equilibrium pressure in seawater is more higher than that in pure water, and methane hydrate could be formed rapidly during pressurization if the subcooling is maintained at 9K or above in seawater and 8K or above in pure water, respectively. Also, amount of consumed gas volume in pure water is more higher that in seawater at the same experimental conditions. Therefore, it is found that NaCl acts as a inhibitor.

• 한국태양에너지학회 논문집
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• 제21권1호
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• pp.71-82
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• 2001

The heat transfer experiment in a latent heat storage tank as a solar energy storage system for the hot water supply was carried out. The latent heat storage tank was consisted of triple - tube type ; Outer shell for hot water from solar collector, PCM storage vessel in the middle of the tank and inside tube for hot water recovery. The heat storage tank has the dimension of 60 cm long and 34 cm outside diameter. Paraffin wax(m.p = 55.4C) and sodium acetate trihydrate(m.p = 58 C) were employed as the PCM this study. Experimental variables were inlet temperature and flow rate of the hot water for heat storage stage and cold water for heat recovery stage. Temperature profiles, heat transfer coefficient and the efficiency of heat storage$(Q/Q_{max})$ and heat recovery $(Q/Q_{max})$ were determined for the paraffin wax and inorganic salt respectively.

• 한국태양에너지학회 논문집
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• 제21권1호
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• pp.83-91
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• 2001

The heat transfer experiment in a pilot scale latent heat storage tank as a solar energy storage system for the hot water supply was carried out. The latent heat storage tank was consisted of three parts; Outer shell for hot water from solar collector, PCM storage vessel in the middle of the tank and immersed coil in the PCM vessel for hot water recovery. The heat storage tank has the dimension of 115 cm in height and 32 cm outside diameter. Paraffin wax (m.p = 55.4C) and sodium acetate trihydrate (m.p = 58 C) were employed as the PCM this study. Experimental variables were inlet temperature and flow rate of the hot water for heat storage stage and cold water for heat recovery stage. Temperature profiles, heat transfer coefficient and the efficiency of heat storage $(Q/Q_{max})$ and heat recovery $(Q/Q_{max})$ were determined for the paraffin wax and inorganic salt respectively.

• 상하수도학회지
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• 제19권2호
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• pp.144-148
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• 2005

The industrial development of large scale deep bed filters has been a very important step in the process of drinking water production and more recently in the tertiary treatment of wastewater. The target of deep bed filtration is the retention is the retention of small particles generally smaller than 30 microns at relatively small concentration, generally less than 30 mg/l from natural water (surface water or aquifers) or secondary treated wastewater. The relation between the retention efficiency and the characteristics of the particles has been extensively studied experimentally and through different models of retention. During the last years the development of new technologies (fiber filter, membrane modules) lead to more intensive processes compared to conventional sand filtration. Fiber filters can combine intensification with a decrease in specific energy needed however they cannot be operated under gravity like sand filters. Membrane filters (UF or MF) are much more intensive and efficient than sand filters. The specific energy needed is not so high (about $0.1Kwh/M^3$) but is higher than sand or fiber filter. A Life Cycle Analysis (LCA) has to be made for a complete comparison between these technologies taking in account that the efficiency of particle retention obtained by membrane filters is unique.