• Title/Summary/Keyword: Membrane system

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Performance Test of PEMFC with Hollow Fiber Membrane (중공사막 가습에 따른 PEMFC의 성능 평가)

  • Lee, Ho-Yeol;Chon, Kwang-Wu;Park, Chang-Kwon;Oh, Byeong-Soo
    • Journal of Hydrogen and New Energy
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    • v.16 no.1
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    • pp.82-91
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    • 2005
  • Polymer membrane needs to maintain appropriate moisture. Insufficient moisture causes low conduction of hydrogen ion because of increased contact resistance between electrode and membrane by shrinking membrane, and abundant moisture decreases fuel cell performance as difficulty of diffusion reacting gas. Therefore, water controlling system is very consequential for the polymer membrane fuel cell. If hollow fiber membrane humidification is used between fuel and air lines, it is possible to supply heat to fuel and air by using thermal exchanger. It can supply appropriate humidity depending on operating temperature, and can recover heat from exhaust gas which contains water vapor and air. Because of simple structure of humidification system, this system can be easily applied in the PEMFC and cut down cost.

Nonlinear Analysis of Curved Cable-Membrane Roof Systems (굴곡형 케이블-막 지붕 시스템의 비선형 해석)

  • Park, Kang-Geun;Kwun, Ik-No;Lee, Dong-Woo
    • Journal of Korean Association for Spatial Structures
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    • v.17 no.3
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    • pp.45-55
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    • 2017
  • The objective of this study is to estimate the mechanical characteristics and nonlinear behaviors on the geometric nonlinear analysis of curved cable-membrane roof systems for long span lightweight roof structures. The weight of a cable-membrane roof dramatically can reduce, but the single layer cable-membrane roof systems are too flexible and difficult to achieve the required structural stiffness. A curved cable roof system with reverse curvature works more effectively as a load bearing system, the pretension of cables can easily increase the structural stiffness. The curved cable roof system can transmit vertical loads in up and downward direction, and work effectively as a load bearing structure to resists self-weights, snow and wind loads. The nonlinear behavior and mechanical characteristics of a cable roof system has greatly an affect by the sag and pretension. This paper is carried out analyzing and comparing the tensile forces and deflection of curved roof systems by vertical loads. The elements for analysis uses a tension only cable element and a triangular membrane element with 3 degree of freedom in each node. The authors will show that the curved cable-membrane roof system with reverse curvature is a very lightweight and small deformation roof for external loads.

Effect of elevated air temperature on shell-and-tube Nafion membrane humidifier in PEMFC system (PEMFC시스템의 공기 공급 온도 변화에 따른 중공사형 나피온 막가습기의 성능특성)

  • Yoon, Jae-Eun;Jang, Hyo-sun;Hwang, Jun-Young;Kang, Kyung-Tae
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.345-348
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    • 2009
  • Maintaining proper membrane humidity is crucial to ensure optimal operation of a PEMFC system. A gas-to-gas membrane humidifier is popular technology for external humidification of PEMFC reactant gases. Characteristics of heat and water transfer in shell-and-tube Nafion membrane humidifiers has been experimentally investigated for various dry side inlet temperature of membrane humidifier. The results show that heat flux decreases linearly with dry side inlet temperature of membrane humidifier. The water flux through the membrane varies nonlinearly with the temperature elevation.

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Sound Absorption Characteristics of Permeable Membrane (통기성을 갖는 막재료의 흡음특성)

  • Jeong, Jeong-Ho;Kim, Jung-Joong;Kim, Ku-Je
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.10a
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    • pp.270-275
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    • 2009
  • Sound absorption characteristics of membrane system which are used in stadiums and arenas were investigated. Theoretical studies on acoustic properties of single and double leaf permeable membrane conducted. Also, experimental studies on sound absorption characteristics of combined membrane system that is composed of outer and inner membrane material were conducted. In this study, sound absorption characteristics of each membrane were investigated by experiments in reverberation chamber. 4 types of permeable membranes and a non-permeable membrane were used for experiments. Air space behind membrane material and tension on the membrane was varied. Sound absorption performance of permeable membrane materials was confirmed. As increasing air space behind the membrane material, sound absorption coefficient was increased. In a resonance absorption frequency band sound absorption coefficient varied more dramatically. Sound absorption characteristics were flat in mid and high frequency range and sound absorption coefficient was from 0,3 to 0,5. Also sound absorption coefficient was increased by the increment of surface density and air permeability of membrane. However, over the certain value of air permeability, sound absorption coefficient was decreased. These results can be used as design factors and method for the room acoustic design of dome-stadiums and large free-form buildings.

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Lake Water Treatment using Ceramic Ultrafiltration Membrane System with Periodic Water-backflushing

  • Park, Jin-Yong;Kyung, Gee-Yong;Han, Song-Hee;Kim, Hyun-Woo;Lee, Hyuk-Chan
    • Korean Membrane Journal
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    • v.8 no.1
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    • pp.50-57
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    • 2006
  • We treated lake water by ceramic ultrafiltration membranes and found the optimal backflushing period and trans-membrane pressure (TMP) of periodic water-backflushing system. The optimal filtration time interval at fixed BT = 3 sec was 30 for A002 membrane in all viewpoints of $J/J_0,\;R_f$, and $V_T$, and we could acquire the highest $V_T$ value in the membranes used here. However, the highest $V_T$ was acquired at FT = 60 sec for M9, and at FT = 90 sec for C005 membrane. Then the lower TMP reduced the membrane fouling during filtration of lake water, and could maintain the higher permeate flux compared with the initial flux. However, the largest value $V_T$ could be obtained at the highest TMP condition for M9 membrane at fixed FT = 60 sec and BT = 3 sec. The quality of treated water in our UF ceramic system was Turbidity = $0.20{\sim}4.88NTU$, $COD_{Mn} = 0.00{\sim}2.58 mg/L$, $TDS = l8{\sim}71 mg/L$, and $NH_3-N = 0.004{\sim}1.689 mg/L$.

Resonance and Response of the Submerged Dual Buoy/Porous-Membrane Breakwaters in Oblique Seas

  • Kee, S.T.
    • Journal of Ocean Engineering and Technology
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    • v.15 no.2
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    • pp.22-32
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    • 2001
  • The numerical investigation of obliquely incident wave interactions with fully submerged dual buoy/porous-membrane floating breakwaters placed in parallel with spacing is studied based on linear potential theory and Darcy's law. The numerical solutions are obtained by using a discrete-membrane dynamic model and second-kind modified Bessel function distribution over the entire boundaries of fluid regions. First, numerical solutions for an idealized dual submerged system without buoys are obtained. Second, a more practical dual submerged system with membrane tension provided by buoys at its tops is investigated by the multi-domain boundary element method particularly devised for dual buoy/porous-membrane problems with gaps. The velocity potentials of wave motion are coupled with porous-membrane deformation, and solved simultaneously since the boundary condition on porous-membrane is not known in advance. The effects of varying permeability on membranes and wave characteristics are discussed for the optimum design parameters of systems previously studied. The inclusion of permeability on membrane eliminates the resonances that aggravate the breakwater performance. The system is highly efficient when waves generated by the buoys and membranes were mutually canceled and its energy at resonance frequency dissipates through fine pores on membranes.

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Determination of Low-temperature Electrochemical Properties of Selected Cation-exchange Membranes for Cathodic Protection Analysis

  • Ko, Moon-Young;Kwon, Byeong-Min;Hong, Byung-Pyo;Byun, Hong-Sik
    • Korean Membrane Journal
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    • v.10 no.1
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    • pp.8-12
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    • 2008
  • The electrochemical properties of Nafion type membranes as a function of temperature to examine the key factors affecting the cathodic protection process at low temperatures was investigated in this study. Variable temperature experiments for AC impedance, DC resistance were conducted. The resistances of 3 Nafion membranes (N 324, N 450, N MAC) were measured in 30% KOH (aq) for a range of temperatures between $-30^{\circ}C$ and room temperature. Membrane resistance increases exponentially with decreasing temperature. This behaviour is most significant at operational temperatures below $0^{\circ}C$. These membranes are stable under the low temperature and caustic conditions of the heat exchange system, but they place a much higher restriction on the cathodic protection of the stainless heat exchange stack. N 450 has the lowest AC impedence and DC resistance at temperatures below $0^{\circ}C$ and consequently is most suitable membrane of the three, for low temperature applications.