Hyung-Man Kim

Theoretical analyses of autothermal reforming methanol for use in fuel cell

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

An Experimental Study of Scale-up, Oxidant, and Response Characteristics in PEM Fuel Cells

It is important for fuel cell to become flexible in order to accommodate the situations of application areas for reducing costs and expanding coverage. Scale ups in series and parallel to 1-kW class proton exchange membrane (PEM) fuel cell stack are characterized experimentally with oxidant as air and oxygen. Through a serial scaled-up 4-cell stack with an active area of 25 cm² and a parallel scaled-up single cell with an active area of 100 cm², respectively, the 1-kW class 20-cell stack with an active area of 150 cm² per cell is scaled up from the basic unit cell with maintaining their performances. The polarization and power curves of the 1-kW class PEM fuel cell stack with the reactants H₂/air and H₂/O₂ are evaluated. Sufficient power of the PEM fuel cell can operate at flexible nominal current of 40-80 A and nominal voltage of 12-15 V for providing durability and balance between cells. The 1-kW class PEM fuel cell stack is characterized through the comparison of cell voltage differences utilizing H₂/air and H₂/O₂. Both cell voltages with H₂/air and H₂/O₂ follow well the one-twentieth of the responding stack voltages with the small difference.

Green strategy: South Korean energy plan is unrealistic

Dean Griffiths says: Rarely do insights occur after 14 hours of picking colonies. While it may be great for a PI [principal investigator] to publish lots of mediocre papers, students and postdocs require big papers to become established — and constantly working insane hours is unlikely to achieve this. Plus there really are times with your family that you can never get back. Is it worth missing Review boards: all need closer scrutiny

Discrete regenerative fuel cell reduces hysteresis for sustainable cycling of water.

The discrete regenerative fuel cell is being developed as a residential power control that synchronizes with a renewables load which fluctuates significantly with the time and weather. The power of proton exchange membrane fuel cells can be scaled-up adjustably to meet the residential power demand. As a result, scale-ups from a basic unit cell with a 25 cm2 active area create a serpentine flow-field on an active area of 100 cm2 and take into account the excessive current and the remaining power obtained by stacking single cells. Operating a fuel cell utilising oxygen produced by the electrolyser instead of air improves the electrochemical reaction and the water balance. Furthermore, the performance test results with oxygen instead of air show almost no hysteresis, which results in the very stable operation of the proton exchange membrane fuel cell as well as the sustainable cycle of water by hydrogen and oxygen mediums.

Numerical Analysis-Based Design of PEMFC Channel, Fabrication of Channels, and Performance Test Using SU-8

Fuel cells have attracted enormous interest as new power sources because the cells can be used to solve the problem of environmental pollution as well as the natural-resource exhaustion problem. In this study, hydrogen-gas flow in microchannels of different shapes was numerically analyzed to improve the efficiency of a microfuel cell. Flow characteristics in six microchannels of different shapes but under identical boundary conditions were simulated. The analysis result shows that the flow characteristics such as velocity, uniformity, and flow rate, greatly depend upon the channel shape. This implies that the efficiency of microfuel cell can be expected to be increased by adopting the optimal configuration of channel shape for hydrogen-gas flow. The experimental results show that power density of a PEMFC with a microflow channel is higher than that of a PEMFC without a microflow channel; however, a durable catalyst is required in MEA.

Electrochemical Promotional Role of Under-Rib Convection-Based Flow-Field in Polymer Electrolyte Membrane Fuel Cells

Literature data on the promotional role of under-rib convection for polymer electrolyte membrane fuel cells (PEMFCs) fueled by hydrogen and methanol are structured and analyzed, with the aim of providing a guide to improve fuel cell performance through the optimization of flow-field interaction. Data are presented for both physical and electrochemical performance showing reactant mass transport, electrochemical reaction, water behavior, and power density enhanced by under-rib convection. Performance improvement studies ranging from single cell to stack are presented for measuring the performance of real operating conditions and large-scale setups. The flow-field optimization techniques by under-rib convection are derived from the collected data over a wide range of experiments and modeling studies with a variety of components including both single cell and stack arrangements. Numerical models for PEMFCs are presented with an emphasis on mass transfer and electrochemical reaction inside the fuel cell. The models are primarily used here as a tool in the parametric analysis of significant design features and to permit the design of the experiment. Enhanced flow-field design that utilizes the promotional role of under-rib convection can contribute to commercializing PEMFCs.

Performance Evaluation of PAN Nanofiber Air Filter Fabricated by Electrospinning

* Dept. of Electronic, Telecommunications, Mechanical and Automotive Engineering, Inje Univ. (Received June 10, 2015 ; Revised September 2, 2015 ; Accepted September 16, 2015)Key Words: Nanofiber(나노섬유), Electrospinning(전기방사), Polyacrylonitrile(폴리아크릴로니트릴), Heat Roller(히트롤러)초록: 나노물질은 작은 크기와 공기필터 응용장치의 초고표면적과 함께 기계적, 물리적, 화학적 특성을 가진다. 전기방사는 나노섬유 중합체를 제조하는데 있어 가장 효율적인 기술로 인식되어왔다. 최적의 제조 조건을 찾기 위해, 여러 전기방사 공정 파라미터의 효과에 따른 폴리아크릴로니트릴(PAN) 나노섬유의 직경, 성향 및 분포를 분석했다. 층간파괴 인성 향상시키고 히트롤러로 적층된 부직포의 형태로 박리를 억제하고, PAN 나노섬유 공기필터의 여과효율과 압력강하 성능을 실험적으로 평가하였다. Abstract: Nanomaterials possess unique mechanical, physical, and chemical properties. They are small, and have an ultrahigh surface area, making them suitable for air filter applications. Electrospinning has been recognized as an efficient technique for fabricating polymer nanofibers. In order to determine the optimum manufacturing conditions, the effects of several electrospinning process parameters on the diameter, orientation, and distribution of polyacrylonitrile (PAN) nanofiber are analyzed. To improve interlaminar fracture toughness and suppress delamination in the form of laminated non-woven fibers by using a heat roller, the performances of filter efficiency and pressure drop achieved with PAN nanofiber air filter are evaluated experimentally.

Experimental Study on Autothermal Reformation of Methanol with Various Oxygen to Methanol Ratios for Fuel Cell Applications

OH는0.23이었으나실험결과는30 % 높은0.30일때최적의성능을나타내었다. 이것은혼합기체의농도차이, 반응속도, 촉매, 반응기의열손실, 반응시생성된생성물등의변화때문인것으로여겨진다.Abstract: The use of Hydrogen as a fuel is receiving considerable attention and as a result, research on novel methods ofhydrogen production is necessary so that the hydrogen demands in the future can be satisfied. This study presentsexperimental data on methanol Autothermal Reformation that quantifies the relationship between the oxygen-to-methanolratio (O

The effect of relative hydrogen concentration on catalytic reaction over platinum under low gravity condition

Experiments were performed under low gravity condition in order to investigate the surface reaction model. A spherical platinum of 1.5 mm in diameter was used, and the surface temperature was measured by thermocouple. The mole fraction of nitrogen of the mixture was 0.91. As the effect of natural convection can be neglected under low gravity condition, the governing equations of mass, energy and species concentrations are formulated in one-dimensional polar coordinates. Axial symmetry, zero azimuthal velocity and no gradient along the axis are assumed. The low gravity condition of the present experiment was realized by the parabolic flight. The relative hydrogen concentration of the mixture was varied. If the relative hydrogen concentration is larger than 0.23, the numerical results simulated the experimental results successfully. However, at relative hydrogen concentration less than 0.23, the numerical results did not explain the experimental results well.

Ignition of Methane-Air Mixtures by Isothermal Hot Wires.

Hot surface ignition of methane-air mixtures has been experimentally studied in normal gravity and microgravity. The primary aim of this research is to explain the effects of natural convection and catalytic reaction on the hot surface ignition in a closed vessel. The hot surfaces used are platinum wire for catalyst and nickel wire for non-catalyst. In order to define the initial condition and make the analysis simple, the following control unit was developed; which heats the wire to the setting temperature in a very short time, and maintains the wire temperature constant until ignition. From experimental results, ignition temperatures with platinum wire are higher than those with nickel wire by the catalytic inhibition of ignition due to the reactant depletion on the surface of the wire. Ignition temperatures with platinum wire are highest near the stoichiometric mixture ratio and decrease with equivalence ratio depart from stoichiometric mixture ratio, while those with nickel wire increase with equivalence ratio. Ignition temperatures in normal gravity are higher than those in microgravity. Natural convection supplies reactants to the platinum wire surface, and therefore reactants are consumed because of promoting catalytic reaction in normal gravity.