• 전기화학회지
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• 제11권4호
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• pp.227-241
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• 2008

This article involves a unified treatment of equilibrium thermodynamics of the chemical reaction coupled with other interfacial (phase boundary) reactions. The modified (restrictive) chemical potential ${\mu}_k^+$, such as electrochemical potential, hydrostatic-chemical (mechanochemical) potential (exceptionally in the presence of the pressure difference) and surface-chemical potential, was first introduced under the isothermal and isobaric conditions. This article then enlightened the equilibrium conditions in case where the release of chemical energy is counterbalanced by the supply of electrical energy, by the supply of hydrostatic work (exceptionally in the presence of ${\Delta}p$), and finally by the release of surface energy, respectively, at constant temperature T and pressure p in terms of the modified chemical potential ${\mu}_k^+$. Finally, this paper focussed on the difference between chemical and electrochemical equilibria based upon the fundamentals of the isothermal and isobaric equilibrium conditions described above.

• Journal of Advanced Marine Engineering and Technology
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• 제39권10호
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• pp.1062-1067
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• 2015

Floating architecture is a type of building that is geographically located on a sea or a river. It floats under the influence of buoyancy, and does not have an engine for moving it. Korea is a peninsula surrounded by sea except on the north side, so floating architectures have been mainly focused on two points: solving the issue of small territory and providing various leisure & cultural spaces. Floating architectures are expected to save energy effectively, if they use sea water heat, which is known to be clean energy with infinite reserves. To use sea water heat as the heat source and/or heat sink, this study proposes a model in which a sea water heat exchanger is embedded in the concrete structure in the lower part of the floating architecture that is submerged under the sea. Based on the results of performance evaluations of the sea water heat exchanger using CFD (computational fluid dynamics) analysis and mock-up experiments under various conditions, it is found out that the temperature difference between the inlet and outlet of the heat exchanger is in the range of $3.06{\sim}9.57^{\circ}C$, and that the quantity of heat transfer measured is in the range of 3,812~7,180 W. The CFD evaluation results shows a difference of 5% with respect to the results of mock-up experiment.

• 자원환경지질
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• 제24권3호
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• pp.219-226
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• 1991

High quality quartz crystals are grown in 0.5N NaOH + LiOH solution on the seed crystal at $370-395^{\circ}C$ and $1200-1300kg/cm^2$ condition. Growth rates are determined by the crystal thickness grown on the seed crystals with Z(0001) and X($11\bar{2}0$) direction. Relatively high growth rate of Z(0001) direction gradually changes as the temperaure difference (${\Delta}$ Ti) between growth and dissolution zones from 25 to $10^{\circ}C$. The X axis direction is affeced by ${\Delta}$ Ti, and +X($11\bar{2}0$) direction shows a high growth rate than -X($\bar{1}\bar{1}20$) direction. According to the variation with kinds of solutions used, the crystal growth that in NaOH solution is found to be slower than that in $Na_2CO_3$ solution. However, for the case in the NaOH solution mixed with LiOH, it shows a favorable growth rate in terms of grown crystal quality.

• 한국항공우주학회지
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• 제40권11호
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• pp.1010-1015
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• 2012

본 연구에서 폐열 에너지를 수집하여 직접 전기로 변환하는 박막형 열전지를 제작하였다. 전도성 탄소섬유에 탄소나노튜브를 코팅함으로써 전기 전도도는 증가하였고, 다양한 곡률 반경에 대한 굽힘 실험에서 전극의 저항변화는 없었다. 열전지의 최대출력은 온도차의 제곱에 비례하여 증가하였으며, $3.4^{\circ}C$의 온도차에서 2.5 mW/kg의 전력을 생산하였다. 12시간의 방전 실험 결과, 열전지는 지속적으로 구동이 가능함을 확인하였다. 또한, 유연한 열전지를 뜨거운 유체가 흐르는 파이프에 감아 구동한 결과, 파이프의 곡률반경에 따라 내부저항은 감소하였고, 생산된 전력은 최대 30 % 상승하였다. 따라서 제작된 열전지는 다양한 곡면형 열원에 적용이 가능하다.

• 한국태양에너지학회 논문집
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• 제25권4호
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• pp.37-44
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• 2005

An experimental study was conducted to analyze performance of a heating system with variation of control logic of the system. The system uses a solar as heat source and composed with heat pump that uses R-22 as working fluid. The difference between the developed system and the commercially available heating system is working fluid. The solar assisted heating system which was widely distributed in the market uses water as a working fluid. It could be freezing in case of the temperature drops down under freezing point. The anti-freezing fluids such as methyl-alcohol or ethylene-glycol are mixed with the water to protect the freezing phenomena. However, the system developed in this study uses a refrigerant as a working fluid. It makes the system to run under zero degree temperature conditions. Another difference of the developed system compare with commercial available one is auxiliary heating method. The developed system has removed an auxiliary electric heater that has been used in conventional solar assisted heating system. Instead of the auxiliary electric heater, an air source heat exchanger which generally used as an evaporator of a heat pump was adapted as a backup heating device of the developed system. As results, an efficiency of the developed system is higher than a solar assisted heat pump with auxiliary electric heater. The merit of the developed system is on the performance increment when the system operates at a lower solar energy climate conditions. In case of the developed system operates at a normal condition, COP of the solar collector driven heat pump is higher than the air source heat exchanger driven heat pump's.

• 한국지리정보학회지
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• 제13권2호
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• pp.94-106
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• 2010

해양온도차에너지(Ocean Thermal Energy : OTE) 개발을 위해서는 에너지 부존 자원량 파악과 개발적지 선정이 선행되어야 한다. 이를 위해 대상해역의 표층과 심층 간의 수온차이 값(${\Delta}T$)에 대한 연중출현확률의 산정이 필요하다. 본 연구에서는 이러한 ${\Delta}T$의 연중출현확률을 산정하기 위해 남해 해역을 대상으로 빈도분석 방법과 조화분석 방법을 사용하였으며, 두 방법의 장단점을 비교하고자 하였다. 비교를 위한 공간적 규모는 OTE 부존량 산정과 연계된 연구지역 전체의 광역적 규모와 적지선정과 연계된 지역적 규모로 구분하였다. 광역적 규모에서는 두 방법으로 산정된 ${\Delta}T$의 연중출현확률 차이를 공간분포 지도로 제작한 후, 확률차이에 대한 면적을 비교하였다. 지역적인 규모에서는 두 방법 모두 연중 출현확률이 가장 높은 지역에서 서로 간의 확률 차이 뿐 아니라, 확률차이가 가장 큰 지역과 작은 지역에서 두 방법의 격월별 출현확률도 비교하였다. 일차적으로 두 방법의 출현확률이 강한 상관성(피어슨 상관계수 r=0.96, ${\alpha}$=0.05)을 보여 두 방법 모두 유용함을 알 수 있었다. 광역적 규모에서 두 방법의 확률차이가 10% 이상 되는 면적은 전체 면적의 5%이하로 나타났다. 따라서 OTE 부존량 산정 시 두 방법 모두 적용 가능함을 보였다. 하지만 현실적으로 다양한 수온 차 조건으로 계산 가능한 조화분석 방법이 보다 적합한 방법으로 판단되었다. 지역적 규모에서 두 방법에 의한 출현확률이 모두 높은 지역에서는 서로간의 확률차이가 약5%이하로 두 방법의 차이가 뚜렷하지 않았다. 하지만 빈도분석으로는 탐지 가능한 10%이하의 확률을 조화분석은 탐지하지 못하는 단점을 보였다. 따라서 OTE 부존량 산정에는 조화분석 방법이, 개발 적지 선정에는 빈도분석 방법이 장점을 지닌 것으로 분석되었다.

• 한국도로학회논문집
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• 제16권6호
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• pp.51-57
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• 2014

PURPOSES : An conventional method for electric power generation is converting thermal energy into mechanical energy then to electrical energy. Due to environmental issues such as global warming related with $CO_2$ emission etc., were the limiting factor for the energy resources which resulting in extensive research and novel technologies are required to generate electric power. Thermal energy harvesting using thermoelectric generator is one of energy harvesting technologies due to diverse advantages for new green technology. This paper presents a possibility of application of the thermoelectric generator's application in the direct exchange of waste solar energy into electrical power in road space. METHODS : To measure generated electric power of the thermoelectric generator, data logger was adopted as function of experimental factors such as using cooling sink, connection methods etc. Also, the thermoelectric generator、s behavior at low ambient temperature was investigated as measurement of output voltage vs. elapsed times. RESULTS : A few temperature difference between top an bottom of the thermoelectric generator is generated electric voltage. Components of an electrical circuit can be connected in various ways. The two simplest of these are called series and parallel and occur so open. Series shows slightly better performance in this study. An installation of cooling sink in the thermoelectric generator system was enhanced the output of power voltage. CONCLUSIONS : In this paper, a basic concepts of thermoelectric power generation is presented and applications of the thermoelectric generator to waste solar energy in road is estimated for green energy harvesting technology. The possibility of usage of thermoelectric technology for road facilities was found under the ambient thermal gradient between two surfaces of the thermoelectric module. An experiment results provide a testimony of the feasibility of the proposed environmental energy harvesting technology on the road facilities.

• 드라이브 ㆍ 컨트롤
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• 제16권2호
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• pp.66-71
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• 2019

In this study, flow analysis and dehumidification experiments were performed on hollow fiber membrane module to confirm the dehumidification characteristics for its different configurations. The CFD for the three different models was conducted using $30^{\circ}C$ temperature and 30%RH inlet humidity for quantitative analysis. Each model has different shape parameters i.e. the number of baffles. Comparison between flow analysis results and dehumidification experiment results revealed a percentage error of about 5%. The difference in relative humidity between the inlet and outlet for each model was calculated using flow analysis data. It was established that the difference in relative humidity of the inlet and outlet for the refined model with three baffles was highest among the three modeled modules of hollow fiber membrane module, i.e. around 9%.

• 한국수소및신에너지학회논문집
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• 제28권1호
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• pp.56-62
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• 2017

Although most electricity production contributes to air pollution, the vehicle organizations and environmental agency categorizes all EVs as zero-emission vehicles because they produce no direct exhaust or emissions. Currently available EVs have a shorter range per charge than most conventional vehicles have per tank of gas. EVs manufacturers typically target a range of 160 km over on a fully charged battery. The energy efficiency and driving range of EVs varies substantially based on driving conditions and driving habits. Extreme outside temperatures tend to reduce range, because more energy must be used to heat or cool the cabin. High driving speeds reduce range because of the energy required to overcome increased drag. Compared with gradual acceleration, rapid acceleration reduces range. Additional devices significant inclines also reduces range. Based on these driving modes and climate conditions, this paper discusses the performance characteristics of EVs on energy efficiency and driving range. Test vehicles were divided by low / high-speed EVs. The difference of test vehicles are on the vehicle speed and size. Low-speed EVs is a denomination for battery EVs that are legally limited to roads with posted speed limits as high as 72 km/h depending on the particular laws, usually are built to have a top speed of 60 km/h, and have a maximum loaded weight of 1,400 kg. Each vehicle test was performed according to the driving modes and test temperature ($-25^{\circ}C{\sim}35^{\circ}C$). It has a great influence on fuel efficiency amd driving distance according to test temperature conditions.

• 설비공학논문집
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• 제28권10호
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• pp.387-393
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• 2016

A ground source heat pump system maintains a constant efficiency due to its stable heat source and radiant heat temperature which provide a more effective thermal performance than that of the air source heat pump system. As an eco-friendly renewable energy source, it can reduce electric power and carbon dioxide. In this study, we analyzed one year of data from a web based remote monitoring system to estimate the thermal performance of GSHP with the capacity of 3RT, which is installed in a low energy house located in Daejeon, Korea. This GSHP system is a hybrid system connected to a solar hot water system. Cold and hot water stored in a buffer tank is supplied to six ceiling cassette type fan coil units and a floor panel heating system installed in each room. The results are as follows. First, the GSHP system was operated for ten minutes intermittently in summer in order to decrease the heat load caused by super-insulation. Second, the energy consumption in winter where the system was operated throughout the entire day was 7.5 times higher than that in summer. Moreover, the annual COP of the heating and cooling system was 4.1 in summer and 4.2 in winter, showing little difference. Third, the outlet temperature of the ground heat exchanger in winter decreased from $13^{\circ}C$ in November to $9^{\circ}C$ in February, while that in summer increased from $14^{\circ}C$ to $17^{\circ}C$ showing that the temperature change in winter is greater than that in summer.