• Title/Summary/Keyword: low pressure hydrogen

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Development of SMH Actuator System Using Hydrogen-Absorbing Alloy

  • Kwon, Tae-Kyu;Jeon, Won-Suk;Pang, Du-Yeol;Choi, Kwang-Hun;Kim, Nam-Gyun;Lee, Seong-Cheol
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1328-1333
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    • 2005
  • This paper presents the temperature-pressure characteristics of a new SMH actuator using a Peltier module. The SMH actuator is characterized by its small size, low weight, noiseless operation, and compliance similar to that of the human body. The simple SMH actuator, consisting of the plated hydrogen-absorbing alloys as a power source, Peltier elements as a heat source, and a cylinder with metal bellows as a functioning part has been developed. To improve the thermal conductivity of the hydrogen-absorbing alloy, an assembly of copper pipes has been used. It is well known that hydrogen-absorbing alloys can reversibly absorb and desorb a large amount of hydrogen, more than about 1000 times of their own volume. The hydrogen equilibrium pressure increases when hydrogen is desorbed by heating of the hydrogen-absorbing alloys, whereas by cooling the alloys, the hydrogen equilibrium pressure decreases and hydrogen is absorbed. The new special metal hydride (SMH) actuator uses the reversible reaction between the heat energy and mechanical energy of a hydrogen absorbing alloys. The desirable characteristics of SMH actuator, which makes it suitable for the uses in medical and rehabilitation applications, have been also studied. For this purpose, the characteristics of the new SMH actuator for different temperature, pressure, and external load were explored.

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A Study on the Analysis of the Performance and Efficiency of a Low-pressure Operating PEMFC System for Vehicle Applications Using MATLAB/Simulink (MATLAB/Simulink를 이용한 자동차용 상압형 PEM 연료전지 시스템의 성능 및 효율 분석 연구)

  • Park, Raehyeok;Kim, Han-Sang
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.5
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    • pp.393-400
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    • 2013
  • The air supply system has a significant effect on the efficiency of polymer electrolyte membrane fuel cell (PEMFC) systems. The performance and efficiency of automotive PEMFC systems are greatly influenced by their air supply system configurations. This study deals with the system simulation of automotive PEMFC systems using MATLAB/Simulink framework. In this study, a low-pressure operating PEMFC system adopting blower sub-module (turbo-blower) is modeled to investigate the effects of stack operating temperature and air stoichiometry on the parasitic power and efficiency of automotive PEMFC systems. In addition, the PEMFC net system efficiency and parasitic power of air supply system are mainly compared for the two types (low-pressure operating and high-pressure operating) of automotive PEMFC systems under the same net power conditions. It is suggested that the obtained results from this system approach can be applied for establishing the novel operating strategies for FC vehicles.

Heat transfer performance of a helical heat exchanger depending on coil distance and flow guide for supercritical cryo-compressed hydrogen

  • Cha, Hojun;Choi, Youngjun;Kim, Seokho
    • Progress in Superconductivity and Cryogenics
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    • v.24 no.3
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    • pp.62-67
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    • 2022
  • Liquid hydrogen (LH2) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH2 supply system is needed. In the high-pressure hydrogen station based on LH2 currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

Combustion Control through the DME Injection Timing in the Hydrogen-DME Partially Premixed Compression Ignition Engine (DME 분사 시기 조절을 통한 수소-DME 부분 예혼합 압축착화 연소 제어)

  • Jeon, Jeeyeon;Bae, Choongsik
    • Journal of the Korean Society of Combustion
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    • v.18 no.1
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    • pp.27-33
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    • 2013
  • Hydrogen-dimethy ether(DME) partially premixed compression ignition(PCCI) engine combustion was investigated in a single cylinder compression ignition engine. Hydrogen and DME were used as low carbon alternative fuels to reduce green house gases and pollutant. Hydrogen was injected at the intake manifold with an injection pressure of 0.5 MPa at fixed injection timing, $-210^{\circ}CA$ aTDC. DME was injected directly into the cylinder through the common-rail injection system at injection pressure of 30 MPa. DME inejction timing was varied to find the optimum PCCI combustion to reduce CO, HC and NOx emissions. When DME was injected early, CO and HC emissions were high while NOx emission was low. As the DME injection was retarded, the CO and HC emissions were decreased due to high combustion efficiency. NOx emissions were increased due to the high in-cylinder temperature. When DME were injected at $-30^{\circ}CA$ aTDC, reduction of HC, CO and NOx emissions was possible with high value of IMEP.

Numerical study on extinction and acoustic response of diluted hydrogen-air diffusion flames with detailed and reduced chemistry (상세 및 축소 반응 메커니즘을 이용한 희석된 수소-공기 확산화염의 소염과 음향파 응답 특성에 관한 수치해석)

  • Son, Chae-Hun;Jeong, Seok-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1527-1537
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    • 1997
  • Extinction characteristics and acoustic response of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flamelet in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such nonmonotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. The investigation of acoustic-pressure response in each regime, for better understanding of combustion instability, shows different characteristics depending on pressure. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted since flame temperature and chain branching reaction rate decreases as pressure rises. This acoustic response can be predicted properly only with detailed chemistry or proper reduced chemistry.

A Study on the Prediction of Hydrogen Vehicle by the Thermodynamic Properties

  • Han, Sung Bin
    • Journal of Energy Engineering
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    • v.24 no.2
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    • pp.79-83
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    • 2015
  • Hydrogen has long been recognized as a fuel having some unique and highly desirable properties, for application as a fuel in engines. Hydrogen has some remarkably high values of the key properties for transport processes, such as kinematic viscosity, thermal conductivity and diffusion coefficient, in comparison to those of the other fuels. Such differences together with its extremely low density and low luminosity help to give hydrogen its unique diffusive and heat transfer characteristics. The thermodynamic and heat transfer characteristics of hydrogen tend to produce high compression temperatures that contribute to improvements in engine efficiency and lean mixture operation.

Optimization of fabrication and process conditions for highly uniform and durable cobalt oxide electrodes for anion exchange membrane water electrolysis (음이온 교환막 수전해 적용을 위한 고균일 고내구 코발트 산화물 전극의 제조 및 공정 조건 최적화)

  • Hoseok Lee;Shin-Woo Myeong;Jun-young Park;Eon-ju Park;Sungjun Heo;Nam-In Kim;Jae-hun Lee;Jae-hun Lee;Jae-Yeop Jeong;Song Jin;Jooyoung Lee;Sang Ho Lee;Chiho Kim;Sung Mook Choi
    • Journal of the Korean institute of surface engineering
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    • v.56 no.6
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    • pp.412-419
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    • 2023
  • Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh-1, maintaining 99% of its initial performance.

Comparative Thermodynamic Analysis of Organic Rankine Cycle and Ammonia-Water Rankine Cycle (유기랭킨사이클과 암모니아-물 랭킨사이클의 열역학적 성능의 비교 해석)

  • KIM, KYOUNG HOON;KIM, MAN-HOE
    • Transactions of the Korean hydrogen and new energy society
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    • v.27 no.5
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    • pp.597-603
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    • 2016
  • In this paper a comparative thermodynamics analysis is carried out for organic Rankine cycle (ORC) and ammonia-water Rankine cycle (AWRC) utilizing low-grade heat sources. Effects of the working fluid, ammonia concentration, and turbine inlet pressure are systematically investigated on the system performance such as mass flow rate, pressure ratio, turbine-exit volume flow, and net power production as well as the thermal efficiency. Results show that ORC with a proper working fluid shows higher thermal efficiency than AWRC, however, AWRC shows lower mass flow rate of working fluid and lower pressure ratio of expander than ORC.

Behavior characteristics of hydrogen storage vessel(TYPE 1) under gas pressure and temperature conditions using FEM (유한요소법을 이용한 수소저장용기 TYPE 1의 압력과 온도조건에 의한 거동특성 연구)

  • Cho, Seunghyun;Kim, Young Gyu;Ko, Young Bae;Lee, Il Kwon
    • Journal of the Korean Institute of Gas
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    • v.24 no.6
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    • pp.61-69
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    • 2020
  • This paper is a study of the behavior characteristics that occur in the hydrogen storage vessel TYPE 1 according to pressure and temperature conditions by FEM(Finite element method). Von Mises stress (VMS) generated at the highest pressure was compared with Yield strength (YS) of the material for structural safety assessment of the container, and the results of plastic strain energy density (PSED) were analyzed as basic data for life expectancy. According to the analysis results, the safety of the hydrogen gas storage vessel is not ensured due to the occurrence of VMS higher than the yield strength on the bottom of the storage container at a gas pressure of 40 Mpa or higher. In addition, the results of VMS caused by temperature conditions are very low and the behavior by temperature can be ignored. The maximum pressure of VMS/YS below 1 is calculated to be about 30 Mpa, indicating that the hydrogen storage container subject to this paper should be managed with a gas charging pressure of less than 30 Mpa.

Design and Development of SMH Actuator System (SMH 액추에이터 시스템 설계 및 개발)

  • Kwon T.K.;Choi. K.H.;Pang. D.Y.;Lee. S.C.;Kim N.G.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.551-555
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    • 2005
  • This paper presents the temperature-pressure characteristics of SMH actuator using a peltier module. The simple SMH actuator, consisting of the plated hydrogen-absorbing alloy as a power source, Peltier elements as a heat source and a cylinder with metal bellows a functioning part has been developed. The SMH actuator is characterized by its small size, low weight, noiseless operation and a compliance similar to that of the human body. A new special metal hydride(SMH) actuator that uses the reversible reaction between the heat energy and mechanical energy of a hydrogen absorbing ally. It is well known that hydrogen-absorbing alloys can reversibly absorb and desorb a large amount of hydrogen, more than about 1000 times as their own volume. To improve the thermal conductivity of the hydrogen-absorbing alloy, an electro-less copper plating has been carried out. The effects of the electro-less copper plating and the dynamic characteristics of the SMH actuator have been studied. The hydrogen equilibrium pressure increases and hydrogen is desorbed by heating the hydrogen-absorbing alloys, whereas by cooling the alloys, the hydrogen equilibrium pressure decreases and hydrogen is absorbed. Therefor, the SMH actuator has the characteristic of being light and easy to use and so is suitable for use in medical and rehabilitation applications.

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