• 제목/요약/키워드: Counter Mass

검색결과 200건 처리시간 0.023초

인산형 연료전지의 가스유로방향 변화에 따른 열 및 물질전달해석 (Heat and Mass Transfer Analysis of Phosphoric Acid Fuel Cell According to Variation of gas Flow passage)

  • 전동협;정영식;채재우
    • 대한기계학회논문집
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    • 제18권5호
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    • pp.1338-1346
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    • 1994
  • The objective of this study is to investigate the effect of various parameters, such as temperature, mean current density and voltage on the performance of phosphoric acid fuel cell (PAFC) by numerical analysis. Two types of flow passages, which are Z-parallel type and Z-counter type, are evaluated to obtain the best current density and temperature distribution. Parametric studies and sensitivity analysis of the PAFC system's operation in single cell are accomplished. A steady state simulation of the entire system is developed using nonlinear ordinary differential equations. The finite difference method and trial and error procedures are used to obtain a solution.

Effect of Twisted - Tape Tubulators on Heat Transfer and Flow Friction inside a Double Pipe Heat Exchanger

  • Phitakwinai, Sutida;Nilnont, Wanich;Thawichsri, Kosart
    • International Journal of Advanced Culture Technology
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    • 제3권2호
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    • pp.124-131
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    • 2015
  • Computational fluid dynamics (CFD) has been employed for the Heat exchanger efficiency of a counter flow heat exchanger. The Heat exchanger efficiency has been assessed by considering the computed Nusselt number and flow friction characteristics in the double pipes heat exchanger equipped with two types twisted-tapes: (1) single clockwise direction and (2) alternate clockwise and counterclockwise direction. Cold and hot water are used as working fluids in shell and tube side, respectively. Hot and cold water inlet mass flow rates ranging are between 0.04 and 0.25 kg/s, and 0.166 kg/s, respectively. The inlet hot and cold water temperatures are 54 and $30^{\circ}C$, respectively. The results obtained from the tube with twisted-tapes insert are compared with plain tube. Nusselt number and friction factor obtained by CFD simulations were compared with correlations available in the literature. The numerical results were found in good agreement with the results reported in literature.

고효율 응축형 열교환기 개발에 관한 연구 (A study on the development of the high efficiency condensing heat exchanger)

  • 이금배;박상일;박준태
    • 대한기계학회논문집B
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    • 제21권5호
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    • pp.589-601
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    • 1997
  • A computer simulation program of a high efficiency condensing heat exchanger is developed. The flue gas flows outside bare tube bundles both in strong cross flow and in weak counter flow and the cooling water inside the tubes. Condensing heat exchangers achieve high efficiency by reducing flue-gas temperatures to a level at which most of the water vapor in the flue gas is condensed and the latent heat associated with phase change of the water is recovered. The computer model has been verified by comparison with measured data. To verify the model, heat transfer coefficient was adjusted, along with the mass transfer diffusion coefficient and pressure drop coefficient, to achieve agreement between predicted and measured data. The efficiencies of heat exchanger increase 2.3 ~ 8.1% by condensations of 6.3 ~ 62.6% of the water vapor in the flue gas.

IT-SOFC의 전류밀도 및 온도분포에 관한 수치해석 연구 (A Numerical study on current density and temperature distributions of IT-SOFC)

  • 손상호;이규진;남진현;김찬중
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회B
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    • pp.3067-3072
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    • 2008
  • A two-dimensional model for anode-supported IT-SOFCs is proposed in order to accurately consider the heat and mass transport processes with a fully-developed axial velocity profile in channel flow. A comprehensive micro model is employed to describe the electrochemical reaction in anode and cathode of SOFCs. This paper investigates the effects of operational parameters (inlet temperature, the amount of flow rate, and air flow rate) including flow configurations (co-flow and counter-flow) on the current density and temperature distributions in the IT-SOFCs.

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Experimental Study on the Performance of Refrigeration System with an Ejector

  • Lee, Won-Hee;Kim, Yoon-Jo;Kim, Min-Soo
    • International Journal of Air-Conditioning and Refrigeration
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    • 제10권4호
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    • pp.201-210
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    • 2002
  • Experimental investigation on the performance of dual-evaporator refrigeration system with an ejector has been carried out. In this study, a hydrofluorocarbon (HFC) refrigerant R134a is chosen as a working fluid. The condenser and two-evaporators are made as concentric double pipes with counter-flow type heat exchangers. Experiments were peformed by changing the inlet and outlet temperatures of secondary fluids entering condenser, high-pressure evaporator and low-pressure evaporator at test conditions keeping a constant compressor speed. When the external conditions (inlet temperatures of secondary fluid entering condenser and one of the evaporators) are fixed, results show that coefficient of performance (COP) increases as the inlet temperature of the other evaporator rises. It is also shown that the COP decreases as the mass flow rate ratio of suction fluid to motive fluid increases. The COP of dual-evapo-rator refrigeration system with an ejector is superior to that of a single-evaporator vapor compression system by 3 to 6%.

Analysis of Germanium in the Ore Samples by UV-Visible Spectroscopy

  • Reddy, K. Raghava;Lee, Kwang-Pill;Gopalan, Anantha Iyengar;Showkat, Ali Md;Kim, Sang-Ho;Paek, U-Hyon
    • 분석과학
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    • 제17권6호
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    • pp.476-480
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    • 2004
  • A simple, rapid, reproducible and selective UV-Visible spectrophotometric method has been developed for determination of germanium in a week acid medium (pH = 3.0) in the presence of mandelic acid (MA) and malachite green (MG). A single extraction in chlorobenzene was used for the analysis. The germanium-MA ion association complex exhibits an absorption maximum at ${\lambda}_{max}=618nm$ with MG as counter ion and has an apparent molar absorptivtity of $1.313{\times}10^5L\;mol^{-1}\;cm^{-1}$. The values obtained by this UV-Visible spectrophotometric method are in good agreement with the values from inductively coupled plasma-mass spectrometer analysis.

이산화탄소용 핀-관 증발기의 성능해석 (Performance Analysis of Fin-tube Evaporator for Carbon Dioxide)

  • 이민규;김영일;장영수;김용찬
    • 설비공학논문집
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    • 제16권7호
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    • pp.645-651
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    • 2004
  • Fin-tube evaporator for carbon dioxide has been investigated both by experiment and simulation. Inside refrigerant heat transfer and outside heat and mass transfer of a wet surface heat exchanger were modeled using appropriate correlations. The results estimated by the calculation were in good agreement with the experimental results. The simulation errors were less than 7.9% for estimating capacity, 0.6$^{\circ}C$ for air exit temperature, 1.2% for air exit humidity and 17% for $CO_2$ exit pressure. The simulation program was used to study the effect of air flow direction, number of rows and refrigerant circuits. For a 2-row evaporator, parallel flow showed better performance for low air velocity but for high air velocity, counter-flow was better. Refrigerant circuits, however, showed insignificant effect on the performance.

로만 폴란스키의 <테스>: 육체와 자본의 미학 (Roman Polansky's Tess: Aesthetics of Human Body and Capital)

  • 김봉은
    • 영미문화
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    • 제9권1호
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    • pp.71-90
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    • 2009
  • David Harris argues that mass media suppress counter-hegemonic factors in order to reach audience. According to Harris's theory, the success of the film "Tess" depends on its effective adaptation from Thomas Hardy's novel Tess of the D'Urbervilles (1891). Tess (1979), directed by Roman Polansky, casting Nastassia Kinski for Tess, was acclaimed as a professional and commercial success, awarded with various prizes. Hardy's aim at criticizing Victorian English social and moral standard through Tess appears obscure in Polansky's film which focuses on the aesthetics of human body and capital. Polanski's Tess with urban white beauty does not emerge victimized by poverty, which the late twentieth century audience under the capitalist umbrella may abhor. To examine his use of music, sound effect, visual images by means of camera operation—angles, distances, close-ups and frequent movements—light and color, and mythic elements in the film, show Polansky's sharp perception of his contemporary audience's desire and conscientious work upon it.

Ultrastructure of the fertilized egg envelopes in Ancistrus cirrhosus, Loricariidae, Teleostei

  • Dong Heui Kim
    • Applied Microscopy
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    • 제50권
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    • pp.13.1-13.7
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    • 2020
  • We examined the morphology of fertilized egg and ultrastructures of fertilized egg envelopes of Ancistrus cirrhosus belong to Loricariidae using light and electron microscopes. The fertilized eggs formed a mass on the spawning place and were yellowish, spherical, non-transparent, demersal, adhesive, and a narrow perivitelline space. But, the adhesiveness of fertilized eggs was disappeared after spawning excluding contact parts. The micropyle with funnel shape was surrounded by 15-19 furrow lines of egg envelope in a spoke-like pattern. The outer surface of egg envelope has smooth side and inner surface of egg envelope was rough with grooves. Also, the total thickness of the fertilized egg envelope was about 32.58 ± 0.85 ㎛ (n = 20), and the fertilized egg envelope consisted of three layers, an outer adhesive electron-dense layer, a middle layer with low electron density and an inner electron-dense layer with grooves in counter structure from other most teleost. Collectively, these morphological characteristics and adhesive property of fertilized egg, and ultrastructures of micropyle, outer surface, and section of fertilized egg envelope are showed species specificity.

국제 테러리즘의 대응체제 구축방안 (Proposal on for Response System to International Terrorism)

  • 서상열
    • 시큐리티연구
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    • 제9호
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    • pp.99-131
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    • 2005
  • 테러리즘의 최종 목적은 대량살상 자체가 목표이기 때문에 효과적인 테러활동을 억제하기 위해서는 테러의 위협환경과 그 경로를 차단해야 하며, 이에 대한 적극적인 대응방안이 강구되어야 한다. 그러면 위의 위협에 대한 구체적은 대응방안으로서, 첫째, 국제사회는 테러의 근본 원인보다는 테러의 주체, 수단과 방법을 제거하거나, 테러의 대상을 보호하는데 많은 노력을 해온 것이 사실이다. 하지만 향후 테러 방지를 위해서 테러의 발생 원인을 제거하는데 보다 적극적이고 장기간의 노력이 필요하다 하겠다. 둘째, 예방적인 차원의 대응방안이 모색되어야 한다. 테러리즘의 근절을 위해 가장 효과적인방법은 예방이다. 이를 위해서는 테러리즘의 발생원이이 되는 객관적인 환경오소 자체를 제거하고, 테러리스트의 활동 근거지를 추적, 섬멸하여 대량살상무기 및 지원자금의 유입 등을 봉쇄하여 조직을 무력화 시켜야 한다. 셋째, 테러 대응 조직체계를 정립하여 통합된 위기관리기구나 기능이 작동될 수 있도록 장애요인의 지속적인 제거와 국제적 연대를 강화하고, 국내에서 발생 가능한 테러유형을 분석하여, 특성, 대응체계, 전략, 법 적용, 테러피해의 산정, 그리고 대응 프로그램 개발이 시급히 이루어져야 하며, 또한 새로운 테러수단과 양상에 대한 대책수립을 지원할 연구 기반을 구축하고, 이를 활성화시킬 방안이 모색되어야 할 것이다. 넷째, 대(對)테러 대비 총괄적인 정부종합대책 강구를 위해 기관간 업무 분장 등 현장대응체제 발전을 위해 무력테러(행자부), 화학테러(환경부), 생물테러(복지부), 핵${\cdot}$방사능테러(과기부) 등 분야별 테러대응 세부대책을 보완${\cdot}$발전시켜나가야 한다.나 TDT에서는 유의한 차이가 관찰되지 않았다. 또 뚜렛 장애 환아군의 세 가지 서로 다른 유전형 사이에 틱 장애의 가족력, 주의력결핍 과잉행동장애, 강박증, 약물에 대한 반응, 공존 질환 여부 등에 있어서 유의한 차이는 없었다. 결 론:본 연구에 있어 사례 수가 적고 TDT에서 유의한 결과가 발견되지 않았기 때문에 해석에 조심을 기할 필요는 있겠으나, 본 연구는 COMT유전자의 기능적 다형성과 뚜렛 장애 간에 연관 관계가 있음을 밝혀 낸 최초의 보고라 하겠다.산수, 토막짜기 점수도 유의하게 높았다. 약물치료력에 있어서는 임상가가 평가한 약물 반응이 순응군에서 유의하게 높았고, 약물 용량도 순응군이 유의하게 높았으며, 오후 약물 순응율(2003년 3월 평가)도 유의하게 순응군이 높았다. 또한 주치의의 지휘에 따라서도 순응율에 차이를 보였다. 결 론:국내에서는 최초로, 외래 치료를 받고 있는 ADHD 아동에 대한 MPH-IR 순응도를 조사하였다. 평균 1년 치료기간동안의 순응도는 62%로 외국에서의 연구결과와 유사하였으며, 지능이 높을 때, 약물반응이 우수하고, 약물용량이 높으며, 오후약물에 대한 순응이 초기에 높을 때 약물 순응률이 보다 높았다. 결국 약물치료 효과에 대한 만족도가 순응률 결정에 가장 중요한 요인이라고 생각되며, 약물치료효과를 높이기 위한 다양한 전략을 사용하여, 약물 순응도를 향상 시킬 필요가 있다고 생각된다.으나, 주의력에서는 전두엽의 실행능력(executive function)과 관련되는 검사들에서 산소흡입이 특이한 효과를 보여준다는 것이 확인되었고, 기억능력에서는 단기기억능력 평가에서 산소흡입군이 대조군보다 유의한 효과를 보여주는 것으로 평가되었다. 이러한 연구결과는 산소흡입이

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